It's entirely possible I farked up Gunlock somehow. I had to add the main program ROMs and copy some weird numbers from hoot for most of those sets and it was a bit tedious
In the m1data tag, default is the command m1 comes up with if there's no .lst and nothing was specified on the commandline. min is the lowest valid command number (it can be zero) and max is the highest (usually 255 for NeoGeo). If subtype is present it selects the type of Z80 driver (none or zero is the standard SNK driver that 90% of NG games use, 1 is the Technos/Tecmo/Alpha Denshi driver, 2 is the DECO driver, 3 is a later Alpha Denshi driver, and 4 is yet another Alpha Denshi driver.
The Z80 driver ("m1" ROM in SNKglish) goes in the cpu1 region, SOUND1 ROMs from MAME go in samp1, and SOUND2 (if any) go in samp2 (yes, irrmaze gets this wrong, I just noticed ;-) You can largely copy the ROM definitions from MAME's -listxml output, but remove the region="" tags since M1 does that differently