Well I have it configured so that Windows keeps a separate autoexec.bat and config.sys for booting into DOS mode, so DOS should be completely unaffected by whatever the windows drivers do. Though what you mention could definitely be making it behave poorly in Windows mode. To answer your question though, device manager looks good in Win95, except for it showing an unknown display adapter which I have disabled (this is the ATI video; even with its jumper set to off on the motherboard, Windows and Speedsys still detect it for some reason).
I just made the most progress I've made so far in pure DOS. I've been trying a few different versions of GLIDE2X.OVL. The version I had been using is the version from V4.10.01.1600 of the Diamond Monster 3D drivers. With these, running a Glide game in pure DOS results in a solid colored screen and having to hard reset. I also tried the version that came with V2.16 of the official 3DFX Voodoo 1 driver, which I believe is the same exact file (same filesize), and it behaves exactly the same.
I just, however, tried the version of glide2x.ovl from the older V1.08 of the Diamond Monster 3D drivers, and it behaves somewhat better. With the Glide tests, instead of going a solid color and freezing, it immediately returns to the dos prompt, or for the ones that display something to the effect of "Press any key to exit" after the test is done, it skips right to that message. In NASCAR Racing 2, instead of the solid color, it displays the Papyrus splash screen, then goes to the menu, and everything on the menu works until I select Quick Race, at which point it returns to DOS. This is the same behavior that running the 3DFX version in Windows95 was giving me.
Gonna play around with a couple other versions of glide2x.ovl and see what happens.
I've got it working! Tentatively. Tried the glide2x.ovl from v3.00.00 of the Orchid Righteous 3D driver. With the Glide tests, it doesn't show the 3DFX splash screen for some reason, but it does perform the tests themselves properly. With Nascar Racing 2, I had the same issue as above with going to Quick Race when I launched gns3dfx.exe, but when I launched nas3dfx.exe instead, it's working perfectly (it also is weird with the splash screen though; it showed the old-style splashscreen for just a fraction of a second but it instantly disappeared. So not sure if things are working 100%).
I'm able to play the game though, and holy crap is it smoother than software mode. I'll try Screamer 2 in a sec, wanna enjoy making a few crashes of the automotive kind instead of the computing kind 😁
PCs, Macs, old and new... too much stuff.