Hey guys! A few questions about my retro rig I'd like help with!

Hey everyone! A while back I posted about my retro rig and asked for ideas / help with setting it up. Unfortunately, life happened, and I had to take time off of working on my rig. However, now I have time, and I have a few prospective ideas I'd love some help with if you can!

Specs are as follows:

PCChips M598 Super Socket 7 motherboard

AMD K6-2+ OC'd to 550MHz OR Cyrix MII GP333

442MB SDRAM

nVidia GeForce 6200 PCI (something I want to replace with something more fitting to the era - has odd artifacting in Win 98 and Win 2k)

Soundblaster AWE64 ISA sound card

1x 60GB IDE HDD and 1x 40GB IDE HDD

I disable the onboard cache when using the K6 in favor of its much faster L2 cache on die.

Now, my problem is - I'm just not that good at installing and using Win 9x anymore, but wish to learn. My Win 98 install is horrifically unstable. I'll get around to posting the benchmarks I have using ZaffWin, but once I do that I want to wipe the system.

I'd like to get a Win 3.11, 98, and 2k tri-boot, but I understand dual booting different versions of MSDOS is hard. Anyone have any suggestions there? This is to play classic games. Some that only work on win 9x, some that only work on DOS, and so on. What should I replace my graphics card with? Anyone have suggestions on how to go about this system? Much appreciated, thanks!