It is definitely a pain in the ass but I've haven't had any companies as far as I know block my emails yet with my setup. The biggest thing is setting up your dns correctly to prevent your emails from going straight to spam
I was about to write that the Protonmail bridge wasn't that great with serious long standing issues. The main one I experienced myself was the subject line being different than the body for older mails, apparently caused by message UIDs not being stable (issue 220). They did fix that in February so I'll have to check again.
We use disk encryption on all servers to prevent data leak in case the servers are stolen, confiscated or in any way physically tampered with.
Other than that, I think they're not encrypted, but they're also working on Lacre, and they'll most likely start testing it on disroot soon. https://disroot.org/en/blog/tag:lacre