Hand-held foams are fine if you want to bother. But the biggest heat loss--and hence saving--is derived from sealing and insulating the wall above grade and the first four feet below grade.

Is there any reason to seal the bottoms to keep condensation/moisture out? Would it ever run from the top of the wall to the bottom?

The XPS prevents the formation of condensation from interior air reaching the cool foundation walls. At the same time, the foam permits the gradual dispersion of the exterior to interior moisture drive below grade without degrading the insulation itself.

See page 10 in RR-0202 linked below.

Here is a link that might be useful: Building Science Corp. on basement Insulation