I wouldn't be overly concerned about the heat. The panniers (and backpack) are opaque, so you don't get the type of greenhouse heating that afflicts the inside of a car left in the sun. The outer fabric of the panniers will get pretty hot in the sun on the upper surfaces, but the interior temperature won't be much hotter than the ambient outside temperature.

Concerns about vibration can be alleviated with a little cushioning foam placed underneath delicate items. But note that most such damage comes from very sharp, hard raps against the electronic items - such as when they fall directly onto a hard floor. Bumps within a pannier tend to be much softer in character since the bags have quite a bit of give in response to the bike hitting a pothole. I'd be most concerned about items in the pannier bouncing around and hitting each other - so pack in such a way that various items are held in place and there's no loose heavy item that could bump into anything fragile.

The Ortliebs should be completely waterproof, but it's easy enough (and light weight) to add an extra layer of protection from a sealed plastic bag. That way you're also still protected from water damage if the panniers were damaged in some way and got a hole in them.