Okay let me try to help with a few things
Getting the matching rom set while not 100% necessary is the best thing you can do especially if you ROM set is more than a few revisions back.
I prefer the MAME stand alone for a few reasons but they depend on some of my setups like in my room I have both a landscape and portrait monitor and the MAME stand alone emulator handles portrait natively where RA requires you to set the parameter of your screen on portrait it displays in a small rectangle across very little of the screen by default also I use MAME to emulate a few consoles like Atari 5200 Colecovision and a few others and the stand alone version is much more friendly than the RA version when it comes to the MESS side of MAME.
http://docs.mamedev.org/usingmame/aboutromsets.html
This link should explain a lot about the different ROM sets better than I can explain it but I find for myself that the split set is the best one for my needs. That being said the merged set is limited in LB due to LB only having access to the parent zip and not being able to import any clones contained inside an issue that doesn't exist with split and non merged sets.