Test coverage is pretty orthogonal to code review. You might wind up with a large amount of fully tested freshly refactored code that does not meet requirements

Test coverage is pretty orthogonal to code review. You might wind up with a large amount of fully tested freshly refactored code that does not meet requirements or edge cases the tests missed. I'd recommend at least reviewing the test code in your case. Besides that, it sounds like a nice codebase to work in. I've had very good test coverage for libraries and backend services with well-defined APIs I've written, but a lot of my career has been spent doing UI work and I've never found an adequate testing tool that can deal with both the complexity and randomness of human interaction and the rate of change of UI presentation. You can't really regression test UIs, because most UI development intentionally changes the things regression tests look for, so you wind up spending a lot of time updating the regression tests and trying to keep up with UI changes that are being made in a tight code/review/tweak iteration loop.