I disagree. If you have a CRT setup with GroovyMAME, you want to use framedelay 9 whenever possible, and it takes a lot of CPU. Even lightweight systems start to use a decent chunk of CPU with framedelay 9.
Get the fastest CPU you can afford.
Would that be the same advice for a Windows 10-64bit Hyperspin/Mame setup on a LCD or OLED?
Which CPU/GPU, memory, etc.
I want everything to play nice with space to grow.
I think so. With a modern display, it's nice to be able to play new games well, too. Street Fighter 5 is actually pretty demanding GPU wise at 4k. Basically, if you can afford a nice PC, use a nice PC. It's kind of a no brainer.
If you're not using a CRT, I think the highest priority should be getting a variable refresh display. That's going to make an enormous difference in how well these games run. It's so nice to just be able to run anything in MAME at its native refresh and not even worry about fiddling around with settings. It just works.
So that means that you need a somewhat modern GPU (to support GSync or Freesync).
LG has that 48" OLED display with HDMI 2.1 now, and that is a pretty amazing monitor for an emulation setup. You could mount it vertically in an arcade cabinet and have a huge screen (roughly equivalent to a 29" CRT) and a lot of flexibility to do stuff with artwork systems.
Although at this point, it's probably worth waiting until the 3000 series of Nvidia cards comes out. It's going to lower prices on everything across the board, and as of today, there's still no HDMI 2.1 supporting GPU.