The primary sequential issue isn't whether Paul wrote Galatians before or after the Jerusalem council. Instead, the real critical point lies in whether the Men from James/Judea went into Galatia before or after the council.
Traditionally, those whose religious-historical lens fixates on ideology and politics try to argue that Paul would or wouldn't have said such-and-such after James' letter in Acts 15 - as if anyone knows what Paul would, could or should have said! However, some commentators seem to care only about [their view of] Paul's thought, and therefore primarily focus on trying to reconcile his developing rhetoric against James' Jerusalem letter, as against James' famous [eponymous] Epistle
In contrast, those who care to inspect the historical foot paths of all known participants have a larger set of data upon which to base their chronological judgments. That's why this task cannot focus on tracing the ideas of an ongoing conversation, that being the ancient "conversation" between James & Paul (as if there was only one such ongoing conversation, and as if conversations are always progressive and never rehash their old arguments). Most of all, we cannot proceed as if church councils always solve everything when the big wigs throw their weight around. Typically, they don't. They almost never do.
But here are the more likely historical [and scriptural] facts:
The travelling Men from James/Judea had to have an itinerary. From Judea, they either went to Antioch of Syria and then onwards to Antioch-near-Pisidia, or else it must have been the reverse. Now, there were only two routes between Antioch of Syria and Antioch-near-Pisidia, in the mid first century. One could go through the Lion's Gate in Cilicia, or one could go up the Via Sebaste from Pamphylia (as Paul & Barnabas did). Obviously, the same was also true in reverse. But while the routes between Syria and Pisidia were clear and well traveled, as were the trade routes from Judea to Syria, there was no such frequent travel between Judea and Pisidia.
Westward bound ships from Judea only went north of Cyprus during the annual nor'easters, around August, and northern bound ships from Judea would invariably stop at Seleucia (the port of Antioch, Syria) before heading around to (or beyond) Cyprus. But what of Pamphylia? The safe passage granted by Augustus' Via Sebaste was barely 50 years old (give or take) when Barnabas & Paul first trod up its steep paths. That not only means it was a less popular destination; that means it was a less populated destination! There just weren't an awful lot of ships heading purposefully towards Perge or Attalia. Even Paul and Barnabas headed there on a relatively localized shuttle route, probably on a small ship, and almost certainly one of Paul's first three shipwrecks. The point, again, is that Pamphylia would quite naturally have been the Judaizer's far least likely route into Pisidia, and Galatia beyond. Geography alone suggests strongly the Judaizers' route ran: Judea - Syria - Galatia - Pisidia.
Logic, also, suggests strongly that these Judaizers would not have gone from Judea to Galatia without first having heard of Galatia through visiting Syria. Granting, obviously, that these Men from James/Judea were highly motivated to make such a long journey from Jerusalem in the first place, and further granting - as virtually all commentators seem to do - that the Judaizers' trip to Galatia came before the Council of Acts 15, the natural question can be brought back in time to their point of departure. In other words: at the moment when these men first set out from Jerusalem, is it more likely their plans were to head straight for Galatia, or is it more likely they were heading for Antioch? In fact, we do not even know that Judea had heard of Galatian churches before the Council of Acts 15, but we do know that the christians in Antioch, Syria, had all been appraised of the mission to Derbe, Lystra, Iconium and Antioch-near-Pisidia, and we also know this Galatian news came to Antioch some time prior to the visit from these circumcising Judeans.
To sum up so far, it's extremely unlikely these traveling 'Judean-izers' had even heard about Galatia as a region, let alone heard there were gentile believers in towns there, let alone that they would go to Galatia before they would go straight to Antioch. The church in Jerusalem absolutely had heard about Antioch early on, since they'd sent Barnabas up to check on them, about three years or so after Paul's dramatic conversion. Add to that, Peter himself was finally planning a visit to Antioch, Syria. Since the Judaizers happened to reach Antioch after Peter's arrival, it seems Peter's journey itself was actually the strongest impetus for their own decision to travel north in the first place. And, naturally, upon meeting the "christ-ones" in Syria, these Judaizers would not require long to discover (from anyone!) that there were uncircumcised gentile believers in those four towns of Galatia.
For all of these reasons, we should take it as virtually certain that the Judaizers' mission followed a route: Judea - Syria - Galatia - Pisidia.
So much for Geography. Now, at last, for Chronology.*
[Although, technically, none of this is "chronology" properly speaking, but merely "event sequencing". For "chronology" we would need to add dates, or at least estimate time frames. See below.*]
In Paul's letter to Galatia, he says "When Peter came to Antioch...". Now, there was either one visit of Peter to Antioch (Syria) or there was more than one. Several things about Peter's m.o. (in Acts) suggest he did not manage that trip more than once, but those points are circumstantial and largely character based. Nevertheless, what should convince us that Peter only visited once is this. We know the Men from James/Judea went into Galatia criticizing Paul. We know they built up the "mother church" [Jerusalem] as more significant than the Antioch church. We know they compared Paul against the original apostles, and also James the Lord's brother. Given this pattern in Galatians, it appears to be certain that these Judaizers must have also tried to defame Paul by telling a story about how Paul rebuked Peter in Antioch.
But then, given the geography of their itinerary, as concluded above, it appears also to be certain that this visit of Peter was one and the same as the visit in Acts.
In other words, it was the selfsame controversial occasion in Antioch, the one which led Antioch to send representatives down to the Council in Jerusalem - that same occasion covered in Acts 15:1,2 - which also led the Judaizers to head onwards from Antioch and pursue these "Galatians" they'd just heard about.
In other words, the Judaizing of Galatia was happening at the same time as the Council in Jerusalem.
Now, let's review the best reasons for adopting this scenario, and not an alternative one:
At the one time Peter came to Antioch, these Judaizing men from James/Judea were present. Later, in writing Galatians, Paul sets the record straight about his rebuke against Peter only because these notorious Men from James had already told the Galatians a harsh Paul-bashing version of that same story. That, in turn, very strongly suggests that those Men from James had been able to swear, first hand, that they saw Paul rebuke Peter. The Judaizing agenda alone (circumcision as necessary for gentile christians) makes this hypothesis stronger than all other theories.
Against this scenario, it is much harder to imagine the Antioch church being troubled by two separate controversial periods - such as an early one at which Paul rebukes Peter about eating customs, and a later one at which Judaizers rachet up tension to the foreskin level. It is even more difficult to imagine two sets of Judaizers, one working before the Council and one after, or even one Judaizing group that traveled to Galatia without passing through (and causing trouble in) Antioch. Very few were so driven to go so far, as I have said at length elsewhere.
Our primary understanding must be the most likely, that these Men from James in Galatia are extremely unlikely to be anyone but these same Men from Judea in Acts 15. Putting that differently, the Men from Judea, who went up to Antioch and sparked the need for the Jerusalem Council, they are almost certainly the same men who went further on to Galatia. It is therefore highly probable that these Judaizers caused the controversy in Antioch not very long before they knife-vangelized the Galatians. That, in turn, means the Judaizing was going on at about the same time as Jerusalem's council. This, at last, means the Galatian letter must have followed the council.
As I said at the start of this post, chronological* work on Galatians shouldn't be about when we think Paul "would have said" what he wrote in Galatians. Nor should it be about what we think Paul "would have said" in hypothetical letters before or after the Council. No. Much more critically, chronological* work on Galatians should begin with the basic "pre-chronological"* questions of when the Judaizers could have learned about and then traveled into Galatia, whether they went to Antioch first, and whether Peter visited just the one time. To all of these questions, as I have tried to show, the most solid conclusions are that this is precisely what must have happened.
Therefore, Paul's rebuke of Peter belongs at the same time* as the controversial season of Acts 15:1.
Therefore, the occasion of Galatians 2:1-10 refers to the same occasion as Acts 15:1-29.
Therefore, Paul's Galatian Letter was written sometime* after those events, and sometime before the journey beginning with Acts 15:40ff.
*Technically there's no actual "Chronology" in this post because it contains no specific dates for these events. However, chronological sequence is the fundamental element of chronological dating. That makes this post another example of what I've termed "Pre-Chronology". (Blame the Math-teacher brain.)