Got a few questions for those who might have knowledge:

1. Do they actually keep your food stuff cold/cool, even in +90 temps?
2. How long do they keep your stuff cool?
3. I'd imagine that there could be some condensation going on- if so, how bad? Bad enough to avoid putting any sensitive paper or electronics in the main compartment?

I have an Axiom Cortez trunk bag. It will keep my stuff cold/cool for well over an hour or longer. I've never had any condensation. Quite the opposite. Its perfect for insulating electronics from the weather. Particularly cold weather. I carry my camera in mine all of the time. They're quite practical, roomy and you can put whatever you want in them. Mine has the fold down panniers, which is another plus.

I have a Transit that came used with the rack. I love it for shopping. It holds a hot chicken or a cold gallon of milk all the way home. Carries lunch and or a cold drink.

You won't have condensation without a lot of moisture in the air. As long as the bag is kept zipped up, the only moisture will be in the air already inside the bag, which is at most a couple of drops worth.