Is there an easy way to view all changes made to a sandbox environment after a prod refresh?

As a result of the sandbox refresh or changes in sandbox by people after the sandbox refresh? For the former: No. Everything is wiped out completely and there's not even any system notes transferred over from prod. For the latter: run a system notes saved search. You might have to create something separate for certain configuration things, but system notes will catch most activity.

Try this system notes saved search criteria (from my 2019 suiteworld presentation)