@xcom97 Like @quicksilver said, it is mostly the same ROM set, though learning how to use CLRMAMEPRO to verify and build/upgrade a MAME 2003 Plus from your current MAME 2003 set is the advised thing to do.

Nope. No changes before or during launching of the game, with the only change post launch in the RetroArch Quick Menu's Options changing digital and analog to digital-only.

And if you didn't know, MAME 2003 Plus is under Experimental Packages called lr-mame2003-plus.

Also, I should mention I'm on an overclocked RPi3B running a arm_freq=1350 and core_freq=550.

So, if you aren't on a RPi3B+ (that should perform as well if not better since I know the core_freq only has small effect on the emulation I'm doing), then the slowdown you'll encounter might be worse (I forget if Frameskip is available in MAME 2003 Plus like it is in FBA).