Yes, it’s stupid annoying when they don’t read the description or know how to Google, but I feel it’s okay to ask questions to confirm that’s you’re getting what you expect. “Is this compatible with this camera” isn’t always a simple question to answer unless you’re quite familiar with the ecosystem, and even if a person can figure out the answer, it doesn’t hurt to confirm with the seller who may well know the equipment better than you.

Even a question like 'what mount does this use?" - you might have written EF in the description, but if they don’t know that EF is a type of mount then reading the description isn’t enough, and for stuff like lenses the model name is more of a description and it’s easy to get them mixed up.

The ‘right’ temperature is what makes a white object appear white. Of course in practice most ‘white’ objects are not perfectly white, so unless you snapped a grey card it’s quite hard to get it just right, but if it looks right to you it’s unlikely anyone else will notice.