Yes you can select cpu settings in the softmenuII, the mobo will run up to 2.0v, and there are no jumpers except for clear cmos, and something else (I forget), the 100/66 can also be set in softmenu...I belive it reffers to "High" or "low" if you plan to o'c' then set it to high.
The fsb options are not that great...after112 it jumps to 124,133,and 150 and maybe 140(not sure) it has been a long time since I built this one.
AGP can only be set to 1/2
Mem can only be set to cas2,or 3....no interleaving or other mem options.
cDO stepping on your cpu means it is default 100mhz fsb?
I'm not too familliar with Cellies since the 300a, but to give an example my be6 is running a PIII600E @800 6x133 (although I've had it to 957 in an SH6).
Most I've heard of had good luck with the cDO stepping.
I still have mine running, and have the manual handy..so if you need help, you can e-mail me (I can't get to the forum as often as I would like) but I would be glad to help if I can.
Good luck,
Doc