Anything left to consider during the rough in stage?

I'm kind of dizzy thinking about all of this, brush plates, speakers wires running to various terminals, height of TV relative to in wall TV box + mount, comprising optimal viewing height for center speaker etc..

But, I'm currently in the rough in stage and I'm running a CL2 HDMI blue jean cable, 25 foot through Carlon 1 inch ENT conduit. Everything will be playing through the AVR unit, so I can't think of another reason to run more than one HDMI cable. Ethernet port will be near the AVR, so any units/devices I want direct Ethernet for up will be taken care of over there (Xbox, Nvidia Shield, etc).

Any reason to run a second HDMI cable or Ethernet to the TV? I have a second Carlon tube about the same length, might as well run it just in case? This is the in wall box I'm going to use; something to power the TV and brush plate for HDMI cable.

Also, side question: my TV is going to be 77 inches. What should the bottom height of the TV be off the floor while also allowing space for a center speaker about 6.5-7 inches tall?

Much appreciated