Yeah…
This question comes up periodically. You have the sound system, so why choose not to use it 70% of the time? Why not just use it? It’s one button push and makes the setup infinitely simpler.
A programmable remote with activities and such should eliminate the need for hdmi control. I'd leave it off. In fact, it will tend to mess up the remote, because it will change things without the remote knowing it, which will screw up the whole process.
Probably not. Not entirely at least.
I suggest you at least consider always using the receiver for audio. You can get a programmable remote to automate things. It’s just a lot simpler in the long run doing it that way.