I had one of these boards back in the day with a K6-3. A few years ago I hooked it up again and upgraded to a K6-3+. I definitely like the "plus" CPU a lot better. It's cooler, more stable, and clocks both faster and slower with more ease. A K6-2+ is very close to a 3+, and might be cheaper/easier to find (I haven't looked lately). To use those CPUs requires the modded BIOS that Doornkatt referred to.
I wrote a really long and boring post about this board here:
Tyan S1590 (baby-AT Super7) 3.3v AGP power limits
The 2nd post goes through some undocumented Vcore settings. However, it looks like yours is an older revision and maybe it won't go below 2.0V. If you have a multimeter, then you could safely experiment with the jumpers as described in that post (measure with no CPU installed).
The slot arrangement can be inconvenient because it prevents using an AGP card when the board is installed in an ATX case. But as long as you have an AT case with 8 slot openings, then it's no problem.
If you're using an AT power supply then be careful how much 3.3V current you pull. Some AGP cards could overload the onboard regulator and cause damage.
If you use an ATX power supply (and set your jumpers appropriately) then I don't believe this is a problem, but I haven't tried any really heavy cards on mine.
The onboard 3.3V regulator is the heatsinked 3-pin device at the corner of the DIMM slots, near the L2 cache. It gets pretty hot, I started pointing a fan at mine.
Your board has several Sanyo capacitors, which are good, but a couple of the caps near the CPU (the black and gold ones) look like cheapies. The vent pattern looks like Hermei or something. I had those on my board also. I'd consider replacing at least those if you're comfortable doing it.
When I used this board a few years ago, I had some glitchy problems with >32GB hard drive, even though the modded BIOS supposedly allows 128GB (or more?). I don't know if I was doing something wrong but I ended up needing to cap the drive to 32GB and move on with my life.