You’re probably gonna have to experiment a bit. For baking and more delicate things probably the listed fan temp, but for things like roasted potatoes it doesn’t matter as much.

green lacewing.

It is just little tricks for entertainment/practice. So you could do the table smack, but it would be obvious you were casting a spell to do it, and the mark would fade after the spell wore off. It was never really meant to have serious utility. There are feats that can help remove component requirements, which could help with stealth, as it’s usually the verbal/somatic bits that give you away. That being said, being able to douse/light candles and lamps is pretty handy. You can temporarily mark locations or routes for allies, or use the same to confuse or mislead someone, at least within the hour duration. There are probably tons of more creative uses out there if you do a little forum digging.