I self host, on a personal domain I registered in June 2000. Mostly followed a 13?-part tutorial at I think linuxbabe dot com, was the first one that seemed to genuinely be trying to help you set up a good environment, not just as a way to say “doesn’t this sound difficult? Impossible even? Coincidentally you can pay us to do this instead.” Except I put everything on its own VM instead of all on one. (Even a VM for just opendkim, which was maybe not necessary.)

Mostly iPhone mail app and/or Roundcube webmail.

Yes highly recommend it, for receiving email. Greylist blocks like 99.8% of spam. Sending works fine for me, because it’s an old domain with history. I don’t think brand new domains have the same experience.