The single most important thing is putting in conduit between your head end (equipment central location) and the displays. HDMI didn't exist 20 years ago and it won't exist 20 years from now, but your home will still be there and you will need to install whatever is 'new'. Cheaper to run 1.25" conduit today, than to be in trouble a few years down the line.
I agree that installing RUIPro HDMI from your head end to various displays is also a good idea. It cuts down the cost of everything really and allows for true uncompressed 4K video distribution, if that's the goal.
A lot of thought will need to be considered for the video distribution portion as costs for true 4K switchers are a bit exorbitant at this time. But, if that's the goal, then that's the price of admission. If true switching isn't required, then there may be some solid price-conscious options.
I would say the only other things to keep in mind is that any device you want to control should have at least one cat-6 or cat-5e wire run to it. MAKE SURE IT IS PROPERLY LABELED!!! !!!! !!!!! Poorly labeled wiring makes the whole system useless at the end of the day. So label everything properly at both ends.
The combination of surround zones with stereo zones can be a bit problematic depending on your sources, but it can all be taken care of at the head end.
Be careful breaking up equipment locations. If you do have a secondary equipment rack location, make sure there is a conduit feed to the head end so wiring can be upgraded if necessary.
Think for the future! Especially if you are doing the wiring yourself. Wire is cheap, cheap, cheap in comparison to the rest of things. Run wire outside if you ever want to listen while grilling. Run it to the front of the house to listen while gardening. Run it into the garage to listen while mechanicking. I have speaker wiring that allows for all my bathrooms to have audio. I may never use it, but the wire is there just in case I want it. I have 2" conduit from basement to attic so I can always add cabling in the future if I need it. I added wiring to my motorized shade locations. I put in a power supply for them, pulled out the batteries which they had been using, and I now have direct control of them and no longer use the manufacturer supplied remote control. My fireplace is on the system using a wired connection to turn it on and off. My front door lock is controlled through it. And yes, some lighting.
It's not inexpensive to get things done in these setups, and consideration should be made as to whether or not you want 'everything' as part of one integrated system, or you want to just use the application developed by the manufacturer. Things like Nest or Ring are just 'better' for direct control. But, your cable box, receiver, and TV being turned on by one button in a control system is pretty sweet. Just leave the things you don't really need control for off to the side if you want.
For reference: I have a 24 stereo zone setup with two surround areas and a 16x16 video matrix in my home with three full sized equipment racks and Crestron driving the show.
