Cat6a is reasonably priced. But you can run 10Gb on cat5e if needed in future.
I’d probably run some internal fibre for networking servers etc.
Probably hardwire zigbee into all light switches and see if there is a way to have energy monitoring (normally WiFi) on ALL power sockets!
No unless you want to play emulated games docked. The performance hit for aaa games will only work on the 800p screen