Thank you for answering!
Good to know that most things I would need seem to be already working nicely in nextcloud :)
It should respect permissions though, so if you share a file with read access only, they won’t be able to edit it in the editor.
I'll definitely have to try that before trying to send out links.
I'm going to have to test a lot of new android apps, I guess. Thanks for the mentions!
Regarding syncthing, according to gedaliyah's answer here, syncthing will be dropping the android app :(