I dunno, my understanding is that such movements — no matter how broad-based or good at coalition-building they are, at first — tend to purity-spiral like crazy once they're in power.
For one, the communists prided themselves on being an international force where workers' solidarity was paramount, while racial and national distinctions ceased to matter. But did that stop Stalin from deporting "troublesome" ethnic groups, starving several million Ukrainians, or planning a purge of Soviet Jews in his last days? Nope; not even close.
Naturally, that makes me reticent to swear fealty to a populist leader who's likely to exterminate the Swiss for "teeming with globalist banker swine", as well as come for me, my family, my friends, and other insufficiently zealous populists the same way that communist regimes purged "subversives" and "counterrevolutionaries" left, right, and center — no matter how flimsy the charges or how loyal they had proven themselves to be.
After all, Stalin also had people killed by quota, so a populist leader who takes after him and likewise has thousands or tens of thousands of random citizens executed or Gulag'd — so long as it's the right number of people killed, regardless of whether they're actually guilty or not — sounds frighteningly plausible to me.
Per the above, most of us will probably get purged by our comrades if we chose the "winning side". So, really, it's more of a choice between being executed almost immediately (globalists) or being executed in five years' time (populists) — as well as being coerced into doing lots of killing ourselves in the meantime, as well as stare at mass graves filled with corpses that we'll be heaped into ourselves one day. That is, unless you're either blessedly lucky or a
butt-kissing, murderous zealot who curries the boss's favor and whines about how the regime has "gone soft" as soon as their excesses have been phased out.
As such, I'm tempted to say the best move in the game is just not to play and form your own Free State Project or whatever as that "small, but principled and sane" third faction that keeps to itself and stays off the big guys' radar as much as possible. Not an option for everyone, unfortunately, though seeing as "Augustus" won't be available until a generation or two after the initial shit-fight, that's probably your best bet.