If the ball floats it means you hit it with a lot of slice. Racket face is open compared to swing path (high to low).
If you hit the net it means you either close the face (or too closed compared to swing path) or you have a swing path too steep.
In general you should attack a shoulder high ball since you have net clearance and can, if needed, get the ball down towards the opponents feet or find an angle.
If it’s too high, slice is hard (and it should be avoided on low or high balls). It’s better to make a longer flat stroke at the same path how you want the ball to go. Try to keep the racket neutral towards the path.
In theory it’s super simple but if you struggle with a flat shot from a high ball it either means you must practice face control or swing path or a combination.
Think of it as a flatter bajada without the back wall, maybe that helps.
Yes, I struggle keeping the racket face at the right angle. When the ball floats, what seems to happen is the racket face opens just at the moment of impact (maybe my wrist is not locked enough). I'll try to think of it as a bajada...
The ball will have slice regardless (because of the hit and movement) but I suggest you aim for a flat shot.
The best things is honestly a coach with a ball basket and that you film yourself. :)