Latest reference drivers straight off 3dfx should be fine, unless compatibility issues arise. For example, I've found out that Rayman 2's screen resolution picker utility will always crash with anything other than the original, first release drivers when using Win9x!

If you happen to come across issues with specific games you just have to fool around with different drivers. 3rd party drivers are usually there for you to play around with newer games and releases. There was a whole community built around 3Dfx cards at the time they went under. Especially Voodoo5 owners really loved the buggers and held on to them as far as they could, attempting to run much more modern games on them. 3dfxzone.it is the go to place if you want to see odd experiments such as World of Warcraft on Voodoo 4/5 or even Doom 3 on Voodoo2 SLI (a classic!).