I think what you’ve captured is a common issue that testers who move into automation face. What to automate and what not to.
Automated regression testing is about using automated tests to tell us about changes in the application. I.E. if a test fails it means something has changed and then we, as a team, have to explore the change to determine if it is acceptable or not.
So first of all ignore the tools and focus on what areas of the application matter to you the most if they were to change. Spend time understanding how your application works, the technologies it’s made up of and how they connect to one another. Then think about the risks that could affect those parts of the application and how you might test them.
Automation strategies require strong analytical skills and conversations with your team to help you understand your application. But once you know what you want to test and where, the tooling and implementation become a lot easier.