With Australian banks there doesn’t seem to be any problems, if you don’t install gplay, you won’t get notifications though. However I think there were some issues with other countries’ banks, but there’s a list somewhere on the GrapheneOS forums/GitHub for all tested banks.
It really does, but unfortunately they simply have the most secure hardware of android phones. At least you’re just paying for the hardware, but don’t have to continue paying with your privacy (or pack of) if you get Graphene
Sounds like you need to check out Org-roam (if you use emacs) or some other zettelkasten style note taking software