Regarding PRs. I have a an opinion which has become very unpopular since the rise of github.

The way github does PRs is great for open source projects where you have submissions from a very diverse set of developers. You need to evaluate the whole PR as whole and accept it or reject it.

But it is not ideal where you have a small team working on single product. The PR review becomes a gate and it has been my experience as a developer that you spend a LOT of time trying to get your PR reviewed.

My preferred approach is to do smaller and more frequent commits that are merged directly to the main branch. Developers learn to break a problem into very small changes which is a skill by itself. It is the responsibility of a lead or Sr engineer to check the commits as they come so they can provide feedback as soon as possible. This was the spirit of the original continuous integration ideas back in the day.