That TP link outdoor AP is only wireless N, so very slow.
There is also no need to have power at the deck to run WiFi, just run it off the side of our house, WiFi will easily go tens of meters outside, especially with direct line of sight.
If you want to go Ubiquiti, you could stick an AC-mesh (weather proof) on the outside corner of the house and a 6 Long Range in the middle of the house. I think the Poe switched you linked will be fine for Ubiquiti kit.
I’d just terminate all of the cables in the loft with the POE switch and run one back to the ISP supplied router (WiFi disabled) where it comes into the house. No need for a network rack inside the house, that’s major overkill.