Yes TV One is required for 4K viewing. The G3100 does have better range, but there is no guarantee that it will give better wifi in the bedrooms. I personally would stick with the G1100 with wifi disable and get an Orbi mesh system setup in AP mode.
As far as wifi6 and gigabit for one phone and no computer, that is way overkill. Streaming a 4k program only requires 25 mbps. The wifi5(AC) Orbi will be fine. Also as far a range goes, you should never hide routers in a cabinet. They should be out in the open. Hiding inside a cabinet is just one more layer of interference for the signal to travel through.