Can I find best driver (with maximum 3dNow! support)?
What version of Glide2x/3x & ICD more optimazed for 3DNow?
My system: K6-2-550Mhz, LS 5MVP3, 128 PC-100.

MiniGL :
Hm, that should be MiniGL V1.47...
The V1.48 and V1.49 were modified for Athlon 3dNow! compatibility, and are slower on a K6-2.

Glide :
Colourless' GlideXP, as well as Koolsmoky's Glide Files should be the fastest around (I haven't seen Benches comparing both, so not sure which one is faster. But the GlideXP apparently got extremely good MMX and 3dNow! optimizations in the code)

OpenGL ICD's were pretty much fully optimized in the latest Versions. Speed differences between them, you'd have to benchmark yourself.
(Since they are easily replaceable, you could run a small OpenGL Benchmark after copying each version to the Windows\System Directory to find the fastest one for you).

The possibly fastest Driver set all in all should be the x3dfx Series, or the early AmigaMerlin Series (don't know the performance of the current releases).

It is possible to 'customize' each Driver with the DirectX/OpenGL/Glide core Files of your choice, and the most powerful .inf Tweaks (x3dfx Drivers were famous for those). Yet, some Tweaks only work in specific Core File Versions, while they have no (or buggy) effect in others.

That would end you up in creating your own, best Voodoo3/K6-2 Combination Driver, but if seeking absolutely maximum performande, that's the only way ;)

That D3D core is best for K6-2? :-/

Unfortunately I don't have the answer to the best Direct3D Core...

The main item about the Direct3D always was to solve/workaround compatibility issues with newer DirectX8 Games. Which one yields the best performance, I really don't know :(