First, it looks like you’re getting an incredible space, and I’m envious of the experiences you’re setting yourself up for.
Second, I’m reading a ton of mutually conflicting recommendations. Of course, we all have opinions. Most of us have been fiddling with our hobby for decades, filtered out some ideas we don’t like, enhanced ideas we do like, and continue to tweak as we go along. I’d be surprised if you, on completion of the build, didn’t find that there were multiple tweaks that will enhance your A/V experiences.
Sure, plan your dream, but know ahead of time that, even though we mere mortals try to remember all the physics and electronics, mother nature never forgets anything, and there will be some fiddling ahead, and maybe even a lot of fiddling.
As Mike Tyson is reputed to have said, a plan for a fight works well until the first time you get punched in the face.
Now a few specific comments:
Regarding speaker cables, my fronts are studio monitors, which have separate amplifiers for woofer and tweeter, with a low-level active crossover ahead of the amps. This makes the damping factor incredibly high, getting rid of the isolation a high-level crossover brings. That means I had to provide adequate power to the speakers themselves, and that it’s a good idea for those long runs to be balanced. Honestly, though, I don’t know if anyone can hear the difference. They sound pretty good to me, and that’s my baseline - pretty good to me.
Regarding the center channel, I’d definitely put it in. There may well be times when you want it out of the picture, so you should have access to the settings in your receiver to direct signals that would normally go there to the front stereo pair.
For any and all signal cabling, install conduit and make it as big as will fit in the walls. At some point an HDMI cable will crap out (I’ve had two already), and conduit will make replacement much easier. And add a few pipes to places you don’t necessarily feel you’re going to need today, because the tech will change, and ripping out walls to install and wire that overhead screen (who knows?) won’t be an issue.
Have fun with this! I don’t know how much work you’ll be doing yourself, but I’ve found that the more effort you put in, the more rewarding the final experience.