KM's DB and IJN's TB are pretty good (can't say the best as I don't have all the CV lines)
US, RM, KM, IJN fighters are really good due to planes or sailor stats bonus.
For FTs, there are different play styles and each nation is a bit different. Some good at head-on, and some good at chasing or dog fights. It's CV captain's job to play FTs in their best style as designed...
DBs require a lot more practice on manual modes (given you don't suffer lags). It's the best way to counter smaller ships or BBs with wicked small hit boxes.
