Answers

Can't say I've ever heard them doing it when they cool down, but when the sun hits them in the morning, it can happen. If they're mounted to an aluminum facia, that can also transfer noise when expanding/contracting

It is tough to say allthough tt can be normal assuming the gutters/fascia are metal and in an area of the home that receives direct sunlight (enough to cause expansion and contraction).  IMO

Brenda, This can depend on the building materials and the darker the color of the materials. In my experience this seems to be more common with darker colors as they tend to absorb more heat than the lighter ones. I've witnessed this happen with metal roofs, gutters and siding.

Richard Anderson, LeafGuard Exteriors