Question about compatible plug ins

Hey there,
Coming over to the Mac side soon, after 15 years of being on the PC world.

I have a bunch of plug ins, from Steinberg and others that say that they work on OSX, and also with AU versions of the plug in.
Will they work with Snow Leopard?
They are
Plex
PPG Wave
Xphrase
D'Cota.

Also Recycle by propellerhead says it needs to be run under Rosetta.
Will this effect the efficiency of the program in any way?

Thanks for all the help, I'm sure I will have many many more questions!
P