I spent a year on proton and thought the service was pretty good but decided to leave shortly after the tweet drama. Partially for the tweets but partially because I was switching to my own domain and I was asking my friends and family to change my address anyways. Tried a few other services. Here's my 2 cents.

Mailbox.org is good but slow and dated. Tuta is good but seems like it's declining. Posteo is good but dated

I also looked deeper and thought about email encryption. If you email an address that isn't encrypting like hotmail, gmail, etc... Which I was most of the time, the value goes down. Also if you want to use standard protocols with a 3rd party app (calendar, contacts, Thunderbird, etc...) The app needs to support the encryption option or you go with no encryption. Proton only works within their apps or their mail bridge which didn't do calendar. Using something like Signal for secure coms is a better option anyways.

I ended up going with a compromise. Fastmail. Worked with my custom domain, was fast, uses standard protocols (carddav, caldav, etc...), and end-to-end encryption is supported if I want to go that route later.

Its not perfect and costs more than others but it checked off my priorities.

My biggest recommendation is to get 1 or 2 customs domains. 1 for family and friends, and 1 for using with Addy, simplelogin, or ~~Firefox relay~~. This allows you to move email providers in the future without having to change your email address(es). The relay service allows you to hand out addresses like candy to greedy irresponsible websites, and feel safe knowing you can just disable a particular address if that website sells your data or gets hacked.

Edit: Firefox relay doesn't support custom domains