You should install 98 first really, but I'm not even sure you can make 98 install on an sata drive.. you probably can, but good luck.
Anyway you always install the older OS first, and then the next os on a different partition, that way the newer OS's boot loader still works.
You shoudl use fat32 for xp if you want to be able to access that partition from within windows98.
Also - nice link sifugreg, I've been waiting for a detailed way to do that, I figured you could, but its hard to find anyone thats ever written about it.