Alright - first of all, have a look here:
Win98 Socket 939 Voodoo 2 SLi Build! (a.k.a. Glide Overkill)
That's a socket 939 Athlon 64 3800+ running at 2.4GHz under windows 98se. For win98se, you don't need a slow CPU, or a 32 bit only CPU - you can run it on anything as long as you find drivers for the chipset and use sound and video cards with win98 drivers (Geforce 6800 / Radeon x850)
zackoftrades333 wrote: I saw somewhere that one of the last CPUs to support WIN9X was a Celeron 450 or something, but that is 64 bit, and was looking for 32bit so I could run DOS natively.
If you want to run DOS, you should go much slower - socket 370 is good for DOS + win9x 3d games. Then there's the super 7 platform, witch can be slowed down (using a K6-2+ or K6-III CPU) to 386 performance or sped up to Pentium II levels, but those are hard to find. Another alternative to a all-round compatible build is a VIA C3 CPU. They can also be slowed down to 386 levels.
If speed's what you're looking for, a fast LGA 775 Pentium 4 (like the 640 for example) + LGA775 intel i865 mainboard OR Athlon 64 754/939 single core + VIA K8T800 or ULi m1689 is the way to go (these chipsets have great win98 drivers). Nvidia's nforce 3 chipset has win98 drivers as well, but it's not as stable under win98 as the intel, VIA or ULi offerings.
zackoftrades333 wrote:AMD switched to 64 long before that, so all their 32bit CPUs seem slower 😒
If by "32bit stuff" you are refering to the Athlon XP vs Pentium 4, the athlon XP is musch faster clock per clock (example 2.0 GHz Athlon XP 2400+ vs a 2000MHz Pentium 4). Rating wise, an Athlon XP 3200+ is a bit slower then a Prescott running at 3200MHz, but do take into account the fact that the Athlon XP runs at 2200 - 1000MHz slower then the P4. As for the Athlon 64 line, these are faster then their intel counterparts (LGA775 Penitum and Pentium D).
The AMD platform also has the advantage of lower power usage and much lower heat. My win98 LGA 775 build annoyingly uses up one of my 80+ PSUs (enermax nanx 550) witch I could be using on a faster machine, but it just isn't stable with anything else. I also swapped the stock intel cooler for a Deepcool Gammax 300 tower cooler since the CPU would hover around 65-70C in more demanding games. The 939 build on the other hand does well with a 350W FSP PSU + cheap Arctic Cooling socket AM2 cooler I picked up SH from a stores "old CPU cooler box" for 2$. As for socket A vs socket 478 - same rule applies - a 3.2GHz socket 478 prescott needs a beefy PSU and good cooling (I used a Tuniq Tower 120 to keep the CPU at 60C since it ran at 80C with the stock intel cooler) so it's a bit harder to build a reliable machine (but so satisfying). In contrast, a 3200+ Athlon XP will typically run at 60-62C under load (using a quiet Arctic Cooling Copper Lite socket A cooler) and a 350W 80+ PSU with good 5V rails is enough to power most fast socket A builds.
Regardless, both machines perform great, and can run all win9x games at 1600x1200 with eye candy all the way up.

zackoftrades333 wrote:Might have to either patch CPU sensitive stuff, see if I can throttle it really low, or just use dosbox at that point...)
For speed sensitive stuff you either need dos-box, real hardware (486/386) or the aforementioned super socket 7 / VIA C3 build. There's no other way around it.