I use Fastmail way too much to change but I wouldn’t choose it as it’s the most expensive one. The good: you can create any random email for throwaway accounts, the bad: it’s expensive. Mailbox.org is really ugly and their 2FA sucks (last time I checked you had to put the generated number at the end of the password which is weird and annoying) but it’s the cheapest of them all if you take the light account.

If I had to change, I would go for Tuta, Posteo, or Runbox.