You can run win98 on some computers with 32 Megs of memory. I have done it before. But It may need about 128 Megs to run well. Certain programs like a lot more memory. MS Office can run you out of memory fast. Win98 will run pretty well on about 256 Megs or up to 384 to 512 Megs. If you go any higher than 512 Megs, Win98 can not handle the extra memory. It is due to how the OS was written, not the motherboard. Win98 likes at least 384 Megs of free Hard Drive Disk space for swap memory for the windows virual memory system. It runs faster with more free space.
I also recommend getting any available win98 updates from microsoft. With win98SE, I use IE6 with support pack 1. I still run this on motherboards that are older if they can not handle WinXP or I dont want to purchase WinXP. I have found Win98SE with fat32 runs well on 512 Megs of memory.
If you do not like my post feel free to point out your opinion or my errors.