Thank you to everyone for your opinions . Both cards are Manli-branded, so rather lowend, but work smoothly.
Savage is clocked at 110/110, while Vanta 125/125 - Vanta does have 6ns of memory, so it's no problem to overclocked it a bit to the frequencies of standard TNT2, Savage then overcomes, though not significantly. Even Savage would go a bit faster, but I don't know how far and how it would turn out on performance (7ns VRAM).
I was still thinking about Voodoo3 2000 PCI, but to my surprise it is noticeably weaker in 3DM99 than the two cards mentioned (Savage and Vanta over 3000 pts, 35 and 28 FPS vs 1900 pts and 27 and 14 FPS with V3).
So it really seems like the best choice of the aforementioned will be to leave Vanta there.
@Putas:
I read somewhere that the Ali V boards sometimes had trouble getting enough AGP power, so I thought that was my problem, too.
GF2 worked for me in 2D, they passed the 3D test in dxdiag, but in 3DM the computer freezes and a restart is necessary.
I'll try a few more tweaks in the registers that are written about online and see if anything changes.