Is it possible to determine wether my BB is press fit or threaded w/out disassembly? It's XT 8000 if that helps.
If your BB uses a threaded interface, there will be a tool interface.
Frames which use Shimano BB86/BB92 pressfit BBs use a wider BB shell. The pressfit cups will have a thick lip that prevents them pushing deeper into the shell. The shell inner diameter is 41mm, so the diameter of lip should be about 43mm.
Cranksets with 24mm axles can be used in frames originally designed for 30mm axles, either by fitting a special BB whose bearings have a 24mm inner diameter or are sleeved to 24mm, or by fitting an adapter which reduces the shell diameter to allow a normal BB92 or external threaded BB to be used. BB30 shells have 42mm ID; PF30 shells have 46mm ID.
If you have a Trek, you might have a BB95 pressfit BB with shell ID 37mm.