I am using sidecar as well on my iPad Pro... I am playing sims 4 on my iPad via sidecar on my Mac mini
I guess you are talking of using sidecar in mirror mode optimized for sidecar, which is like a remote desktop for home use... the big issue I have with sidecar, which by the way I use a lot at my desk (it's actually the only way I now write on my mini, with my iPad pro magic keyboard, I have stopped using a real keyboard), is that it works well at my desk where I have my mouse, but whenever I move to another room I have no touch screen and no trackpad.... only the keyboard and the pencil, which makes it hardly usable.... There is a clear reason why Apple does not want to add touch functionality but man at least the trackpad, I am not even asking for gestures, just the basic trackpad... So as soon as I move to another room I switch to remote desktop....