Audiobus: Use your music apps together.
What is Audiobus? — Audiobus is an award-winning music app for iPhone and iPad which lets you use your other music apps together. Chain effects on your favourite synth, run the output of apps or Audio Units into an app like GarageBand or Loopy, or select a different audio interface output for each app. Route MIDI between apps — drive a synth from a MIDI sequencer, or add an arpeggiator to your MIDI keyboard — or sync with your external MIDI gear. And control your entire setup from a MIDI controller.
Download on the App StoreAudiobus is the app that makes the rest of your setup better.
iPadOS 15 App Acessibility
I just noticed that iPadOS has a new "Per-App Settings" item at the bottom of Settings–>Accessibility. This lets you override certain settings for a specific app only. For example, if you normally use larger text, and it affects display of an app GUI (like Branches), you can use this to shrink the text back to normal. It's a useful thing to keep in mind.