I never used DGVoodoo so I can't help you with that. However, I can help you with the 800x600, even if it's just barely.
I also had a ton of resolution problems with the game. I don't know the exact resolution off the top of my head, but the best results I managed to achieve was by installing the widescreen resolution patches found at the link below, lowering the monitor resolution to 1024x768 (because otherwise the game refuses to launch), launching the game, and then incrementally increase the resolution in the option screen some notches above 1024x768 so the game is fullscreen (not windowed), widescreen (16 x 9), and the fonts are still comfortably readable without squinting. My fonts have a somewhat anti-aliased look, but I blame this on my plasma 51 inches TV which is not very computer friendly, nor 4K friendly.
I should also mention that I must always lower the resolution to 1024x768 before launching the game (which wreck havoc on my desktop icons) otherwise the game refuses to launch. But once the game is launched, the ingame resolution is a tiny bit better than 1024x768 resolution.
Widescreen resolution patches:
https://www.wsgf.org/node/23149 The site is sadly not very user friendly, scroll down until you see the "Baseline (Widescreen) Solution & Issues", the sentence that follows has the instructions and the download link for the patches.
Hopefully that should improve your situation a tiny bit above the blurry 800x600, but not much further unfortunately. Sorry for not being more helpful than that.