As you switch, I would highly recommend you purchase a domain for yourself, and redirect email from it to your new provider. This separates your "identity" from your email host, so you can switch the latter without having to go through this process again.

If you use a password saving app, that should have some of your login info.

I deleted a Gmail adres I used through college, first I switched the emails of essential accounts like banking manually. Then I manually erased all histories and linked devices. Then follow the FAQ instructions to delete your account. Note it's only "deactivated" for 3 months untill login. Took me a solid 4 hours what was supposed to be lunch.

Wow. That’s the best idea I’ve ever heard. I wish I thought of that sooner, thank you!