I cannot speak to the power requirements of the various batteries out there as I'm no expert, so I'll address your other question about empty Saberforge hilts for DIY projects.
Depending on the hilt, most of SaberForge's designs are modular to some extent now. If you do order an empty hilt for DIY projects, I'd suggest including a note in the order comments asking them not to glue the threaded portions together, because this is something that they do on most of their hilts, except for the pommel areas which are left unglued so you can access the battery/microSD cards.
I recently purchased an old Warrior level Justicar and completely gutted it to install different electronics, and that hilt was all one piece, it was not modular in any way except for the pommel which threaded off.
Hope this is useful to you!