Good question. I tend to base all my miniatures these days. I play a lot of OHW, not got round to WW1 just yet. I would depending on scale, multi base with Crossfire rules in mind as well. So for 15mm and smaller I use 30mm square bases and 20mm to 25mm, 40mm square bases. 28mm would go 50mm or at a push 60mm bases.
I use squares bases but round ones would work as well.
as to the number of castings, again I tend to use Crossfire as a guide here. 3 castings for a rifle armed squad, 4 for a smg squad, 2/3 plus heavy weapon for HMG squad. Squad leader 1 casting, company commander 2/3 castings.
relating this back to OHW, NT only mentions individual castings for his WW2 rules. For me I would , use the above as a guide but have two bases per unit, that way you can include the heavy weapons into a squad.
Alternatively you could base all is individuals and put them on a movement tray. You would still need some way of recording 15 hits….

I’ve got a few multi hit marker bases with 3x7mm dice frames on for this. If you check out my blog you will see an example of a Greek one. (Blog address in signature below)

Good luck and have fun!