Home Ethernet System

[David's8]

The S8 will be moving home shortly and we've been lucky to get a house alongside the 6m x 6m garage that will end its rough sleeping years. (More on that elsewhere later). The issue is that the house is a new build with Cat6 cable run throughout. No ethernet switch is yet fitted. Unfortunately, there is no fibre optic, superfast service available - its "standard" (up to 20mb) over copper line up a 1/2 mile country lane which seems to limit the benefits. Neither of our 2 TVs are "smart" TVs though i currently have a freesat HD box which feeds Netflix etc. I am thinking of getting a streaming music system (Naim Muso). A NAS for back up and storage seems a good idea too.
Questions:
1. Is there any way of improving on the broadband speed?
2. Any recommendations for make/model of switch (im not sure how many ports are needed - will find that out tomorrow)
3. Can/how do you integrate wifi into the system for when you want your portable device to be, well, portable. (Not sure yet if garage has ethernet port)
4. Any suggestions on configuring the system as a whole and any "must-have " gizmos"

Really appreciate any help in making the best of this system