I'll take a stab at your questions although I'm no expert.
I use the AW 18350s and 18650s (nipple top) that I've used with all my other mods. I *believe* flat tops will work as well, based on the spring and positive post design in the Orion. In any case, it's a VW device and will not fire if the battery doesn't work.
I get my wire from ebay and stainless wick sheets from OK City Vapes but you can get them anywhere. I wouldn't recommend getting pre oxidized wicks, it's easy to do yourself and you can customize your wicks by doing it yourself.
I've not tried ceramic, I hear they're so fragile many break them just setting them up or your mod falls over and breaks them. They take a while to break in as well. I'm happy with stainless mesh. I've also ran a few tanks with silica 3mm wick on the Orion and it works fine too. Went back to stainless after a day or two because it lasts weeks or months versus days.
I use kanthal awg in 28 and 30 gauges but many swear by the flat wire, I haven't tried it yet though. The 28 kanthal takes a little longer to heat up but keeps it shape longer than 30. I like to be able to pull my wick out for dry burning the gunk off the coils so I like the coil to be thicker and sturdier.
What's great about the Orion V3 (I really love mine) is that it's very easy to check ohms when building coils (one click unlike Provari which requires about 10 button presses every time you want to check the ohms).
The fun of rebuildables is trying all the methods. There's no one best way. It's a journey!
