One of the features seems to be a “hide my email” feature, akin to Apple’s hide my email or Fastmail’s masked email feature.
Having used both of those, I would say one downside is that occasionally, a site will detect that I used the Apple one, which is strange because it’s just an iCloud email address. Perhaps they’re looking for a specific pattern.
I haven’t yet seen the Fastmail one blocked.
One concern with the Proton one is that it seems like its masked emails are all at passmail.com. I’ve already found some sites block protonmail, so they’ll surely block passmail like they do Mailinator and other sites. That could be a limitation that’s less likely to affect Fastmail’s service.
I agree that the bitwarden UI isn’t very good on the desktop app and in the browser extension. I don’t even use the desktop app at all anymore. One positive for protonpass is that the ui is looking pretty streamlined and it feels fast. I think for just the endless regular internet accounts either is fine.
It’s a fair point about small vs. big. I mean security by obscurity doesn’t really seem like a strong point for small, but who knows. I think higher value targets will always end up using the bigger ones anyway.
Important stuff (banking/development secrets) maybe use something like gpg based and offline like https://wiki.archlinux.org/title/Pass or the Qt frontend https://qtpass.org/.