I really like the idea of using Fastmail over Tuta since they support normal protocols and thus third party clients. My main concern is that if they're able to serve those protocols, they have to be able to access my emails in plaintext in some form or fashion, which also means if their systems do (and most likely inevitably will these days) get hacked at some point, all my emails are now exposed and leaked.

+1 to Fastmail, I've used them for almost 8 years now, never ever have I had an issue with them.

Is fastmail better than zoho? I'm have trouble choosing between them to move small org (of 5 people or so).

What's their password manager like?