voodoo1 CAN give some problems/corruption on systems around p2-400 and higher. On a lot of systems it runs fine with most software, even with much higher cpu's. I could not even get a voodoo1 working on my Tusl2-c with 1400mhz P3-S and tried different brands (all working fine on slower systems). Might be the mobo...
The k6-2 is not fast enough to cause any problems, some issues might come from a high fsb (on Intel systems) and that also is not a problem in your case. 400mhz k6-2 is a good cpu to nearly maxxout the voodoo1 (it take a p2-350 to do that and yes, that's a fair bit faster than a k6-2).
asus tx97-e, 233mmx, voodoo1, s3 virge ,sb16
asus p5a, k6-3+ @ 550mhz, voodoo2 12mb sli, gf2 gts, awe32
asus p3b-f, p3-700, voodoo3 3500TV agp, awe64
asus tusl2-c, p3-S 1,4ghz, voodoo5 5500, live!
asus a7n8x DL, barton cpu, 6800ultra, Voodoo3 pci, audigy1