Things don’t crash on me. But bank apps may not work, they usually use play protect and apps with that may not work. Also you will not have root access, it has to do with security but certain apps like titanium backup need root to work. I’ve heard seed vault (built-in backup) isn’t that great but I haven’t used it. I like GrapheneOS, the only annoying thing for me is the lack of notifications for certain apps. That’s pretty much how it goes when you don’t use google on your phone. My workaround is using a separate work profile that has sandboxed google play for apps that I need notifications for.
Yep, google will be able to read your notifications. Which is why I only let things I don’t care about google seeing use the sandboxed google play. Things like games, etc. I use Proton but no notifications for email (and yes I know about the CEO and Trump). That’s more invasive so I just manually check my Proton inbox. You get used to workarounds. I also use a bogus gmail account not tied to me, fake name, dob, phone number, etc. I used juicySMS for it.