Not a true 'PC' since it's not x86 based (if it was x86 based it would be a LOT more demanding to emulate which is why the later IT stuff really isn't going to be run at playable speeds if somebody does tackle it)
but otherwise yeah, very PC-like architecture, including PC video cards, and PC chipsets for a number of things.
one thing MAME doesn't do is emulate the limits of the original Voodoo properly, which tends to result in the emulated Voodoo being able to draw a lot more in a frame than the real one. scenes which cause bad framedrops in MAME are often ones with many, many overlayed transparencies, often full screen. chances are the real card would instead take several frames to draw that, or abandon, causing a lower framerate, or missing graphics on the original hardware at that point, but in MAME, since the limits aren't properly emulated, it slows MAME down instead of the game.
but in general once you get to this kind of system with recompilers etc. there are always going to be points that stutter, especially games that are dynamically loading a lot of content, invalidating caches etc.