Ran 2x18350 for a while, learned I'm not really a fan of other form factors. For regulated mods charge levels shouldn't matter, but the logistics of them heavily limits the options for replacement mods, finding the replacement cells, and possibly chargers. Instead I run quad 18650 nowadays. Not because I need that much power but because I can pop any crap cells in and not worry about them shitting themselves at half charge. Sure the quad boxes are hard to find nowadays but I've got a spare and a box of cells that are still decent enough for dualies. I can just take all of them, along with a $10 half-litre bottle and go completely off-grid for a month.

Also, mesh coil rolls really are the way. Still very cheap, last forever, easy as hell to replace, and as a bonus they heat up and cool down instantly, saving up on liquids.