Try out the free version at first to get a handle on how it all works getting your games and emulators setup.
Yes, if you bought the one year license at 20$ you can upgrade at any point to a lifetime for 30$
As for Mame / Mess and Atari 5200 that actually is not too bad to get setup, it's actually easier now than it used to be. We can help you with getting it setup.