For MAME game data, I think it's about 68GB for roms, unless you tack on the ones that require hard drive images, then it easily goes up to 1TB+ Been awhile since I looked at the actual size of that though. I think it's only my latest build (i7-6700k) that can manage to play the newer Gauntlet games without sound lagging.
I've only really had experience with macOS from work, and it just seems slower in some ways than Linux, and especially slower to get core things updated (like bash). Pretty much in my line of work it was required to install brew, at which point I may as well just use a Linux distribution with yum/dnf/apt, since brew is usually a source compile vs binaries, it's faster with Linux to install things too.
Atari 8Bits: 800xl, 600xl, XEGS, 800, 130xe, 130xe (fully upgraded (soon!))
Atari STs: 1040STf (broken shifter), 1040STe, Mega STe, TT030, Falcon (CT60e, SuperVidel)