@snow_gibbon
For Qoto I actually would recommend trying out the mobile web interface (and just pin that site to your home screen). The web interface is already very mobile friendly.
Qoto is a modified Mastodon server with extra features (see the About page for more info on them) and most apps are made for default Mastodon. You'd be missing out on those extra features, and chances are that some apps don't 100% work nicely with this either.
But if you really want to use an app, I've seen reports that Tusky and Fedilab work fine enough with this server. The official Mastodon app seems a bit problematic apparently.