BRRRRs can be done in any market, as has been noted, but the most important part is the team, who will handle the project from start to finish. Do you have agents or wholesalers who can find good deals and come up with accurate ARVs? Do you have trustworthy contractors that can finish projects on-time and on-budget? Does your PM agree with the rents, and can follow-through on getting them rented? Especially when you're BRRRRing remotely, any one of these "legs of the BRRRR stool" falling short can mean the deal is no longer what you thought you were getting.
With that said, I'm BRRRRing in Oklahoma City, Kansas City, and hopefully Columbus, OH, in the near future. I'd focus more on the team you can put together in a city, vs the specific city itself, to be frank. Lots of cities have good demographics and have opportunities. I'll take a stellar team in a decent city over a mediocre team in a stellar city any day, honestly.