What do you want? Flavor, huge clouds? Many people use many different wraps and coil diameter for various things. It's all about the use, the equipment, and what you're after.
Personally, I'm all about the flavor and massive nicotine delivery. I usually use a 9 wrap 26ga 3mm coil in nearly everything with japanese cotton. Magma, veritas, lemos, sometimes kayfuns. Anywhere from 20-40 watts depending on the juice and what type of flavor I want to be more prominent. For example, suicide bunny derailed, if vaped at 20 watts I get a more prominent natural banana. If vaped at 35 watts I get more of the snickerdoodle flavor and the banana tastes almost caramelized, I love it like that.
You can nearly stick with one coil when you have a variable box mod. You don't have to adjust your coil the adjust the wattage like a mech mod. There's much more to all of it though, but that's what works for me.
Oh, and forget the term sub-ohm unless you use mech mods. It really doesn't matter for the most part unless you are going for super high wattage. The important part is getting good surface area and diameter. For me that's what I listed above, about 1.2 ohms. Heats up decently quick on 20 watts, super quick at 40, awesome flavor all around with good wicking.