When seasoning a cast-iron pan, should you let the oil smoke?
You certainly should let the oil smoke - if you don't, you'll end up with a layer of oil, not a layer of seasoning.
Nothing special happens at 350 F. It is a fairly typical oven temperature, so if you have been looking at guides for oven seasoning, they probably suggest this temperature out of inertia.
I must admit that with my first iron pan, I started out like you, reading a ton of guides, trying to consolidate the information, combining it from knowledge from other sources, and feeling confused. Now, several years and pan purchases later, I would classify such behavior as clear overthinking. There is a wide range of methods (and temperatures) that work, but you do need a bit of hands-on experience to judge how it is going, and intervene if something is not right, and you can't replace it by reading. So just pick one(!) guide, follow it exactly, and use the pan. If the seasoning gets damaged, you will recognize it, and can strip and redo, until you have the skill.