The EvoX BIOS range does not support the additional RAM. X2 range does - use X2 5035 if you can, use X2 4981 otherwise. Note that if you get rid of whatever BIOS the console is currently using, it won't act as a debug console anymore. Consider backing that up before overwriting it (ditto for the files on the HDD).
Supposedly XBMC doesn't use the extra RAM for who knows what reason. This is kinda odd, considering that the devs added the compatibility at one point, but they're the guys who says it doesn't so make of that what you will. It'd be dead handy for those who like to use high quality skins, fan art, high resolutions... The stock 64mb often causes crashes if people try to combine these things together.
I know Surreal uses it, but XXX still doesn't let you set more then 16mb for ROM caching (which is, for example, half the size of Smash Bros, so the emulator still has to use a swap file and still runs that game slow. Just not as bad as it'd otherwise be). I've still got the source code on my PC ready for such time as I can be bothered tinkering with it... Dunno if non-XXX is much better but I do know it handles memory management differently.
Unfortunately the motherboard I upgraded died a few weeks after the upgrade and I went a few months without a console. I've been hesitant to put my new rig at any risk whatsoever because of that, so my personal experience is rather limited.
Run088 has upgraded plenty of systems.
RAM Delimiter is supposedly only for retail games. No one seems to know much about it. Every now and then I do some research but I always end up forgetting.
Garou (the largest NeoGeo ROM in existence, to my knowledge, it's something like 95mb) runs near perfectly under FBA-XXX on a non-upgraded console, so I doubt any other games would benefit from the extra memory. I hear MAME puts it to good use though.
Some 2002 consoles are 1.2 models (256kb TSOP), and a debug console is probably outside the usual rules. If you can boot a game save exploit (such as Krazie's NDure), you can use the dashboard it loads to help determine the version (prior to installing a softmod). NFI if there's anything different when softmodding/flashing debug systems, again, make a ton of backups first.