i don't really do anything different defending against the FB in terms of +/- or double teams. the only difference is the pace is slightly higher, a little more fatigue all around, and sometimes that impacts your approach and stuff. playing a more + or more -, doesn't seem to have much impact on like, allowing more breaks, or creating more turnovers, outside of the way that those things work with any other offense. so nothing special there really.
fastbreak is a lot different than other offenses mostly because it allows scorers to be more effective off ath, spd, bh, and less tied to lp/per. so that kind impacts who on the other team might be scoring, and when you assess how dangerous a scorer is, that should affect your thinking some, too, i suppose. like what might look like a 2 main scorer situation in some other offense, might not be that in fb. but this usually is clear to see in the stats, how your opponent is using them. how you react to who your opponent is using, doesn't change much. but sometimes you can't really rely on history, like early in the season, or in the NT when the guy has a much different regular season lineup. so projections wise, there's some differences.
this is all around the margin stuff though. outside of being aware of the higher pace, you really don't need to treat your fb opponents any differently. fb can draw a bit more fouls too, but still, this is around-the-margin stuff.