You can use RocketLauncher if you want and there are certain benefits to using it, exactly how beneficial is up to you and how much you care about the extra functionality it will give. For me personally I have no use for it but there are others around here who love it for what it can do. You will get very little support in helping set it up from the moderators around here only because most of us do not use it at all. You will have to rely on other users, the RocketLauncher forums or Youtube tutorials on how to set it all up.
There is very few emulators if any that Launchbox won't work with, I can't think of any off the top of my head that don't work but there are a couple that will require some extra legwork like SSF requiring a batch file for mounting disk images or Daphne but they will work.
As for adding games like Xbox, Xbox 360 and PS3 that's up to you. Xbox 360 and PS3 does have emulators at least capable of loading and playing some games at some level.