Though I haven’t bought a catalyst account yet, this is on my agenda - just to say thanks to the developers for their really great work!
If there ever was an app I’d be willing to pay for, then it is this one! 
Just saying this to make clear I haven’t tried version 0.8.13 so far - but my opinion to the points you made:
- I agree - as long as I can configure shortcuts for a task (and this is what I always prefer - when I am writing, I’d ideally not have to leave the keyboard…), I don’t need any buttons at all;
- If you mean the main top bar, I agree - full screen mode should mean “focus mode”, which let’s me focus on the important stuff: writing (or reading…). In case you’re talking of the note top bar, it rather should stay visible, I think… In case I want to rename a note or just check, for example, if it’s currently pinned or not, that shouldn’t force me to leave the full screen mode…