There's no one best option, it's all about fitting your goal.
I have 2X 26g 316L SS/40g Kanthal D fused claptons in my Boreas. I have 2X32g Kanthal A1/40g Kanthal D in my one Diablo, 2X28g 316LSS/40g Kanthal D in my other Diablo, 2X 24g 316SS/40g Kanthal D in my Petri clone, 2X30g 316L SS/40g 316L SS in my Griffin, and 2X 28g Kanthal A1/40g Kanthal D in my Avocado.
My Boreas designed for a higher output, my Griffin/Avocado set ups are for series mechs and the one 32g cored Diablo setup is for my travel piece that I run at 40w. I can actually run that Boreas build in Temp control even without the outer wraps being SS, though sometimes it bumps me out and back to wattage mode.
What I'd suggest to start with would be 28g or 26g cores if you're using SS, then a higher gauge like 36g+ Kanthal to wrap... SS is a bit more expensive and I haven't seen any great deals on wrapping wire like you can find 1000' of the 40g (or 38g) Kanthal D I use for like $10 on Ebay IIRC(which is why most of my builds use that). The properties of the wrapping wire don't really mean anything, you just want some clean wire that's spooled well so you don't have to fight it while trying to build and smaller the gauge the less they affect ramp up. A Boreas build with 26g SS cored Fused claptons should be about .15Ω depending on how well you fill the deck and it's a nice build treating me nicely.