X3000 External Antenna & access points

I am just about to move my x3000 (best router I’ve ever owned) to a recently finished extension.

The plan is to connect it to an external antenna. The new extension has lots of celotex, thus killing the WiFi, so planned to put it in a comms cupboard with an 8 port switch and connect it via cat 6 to some access points.

Does anyone have any suggestions on:

Best external antenna, pole mountable?

Best access points that will allow seamless best coverage to devices moving around the house (I.e. devices pick strongest network strength on same network)?

TIA

Rich

You can purchase third-party SMA interface outdoor 5G antenna with extension feeder.

It depends on the AP device.
Generally can switch seamlessly if support 802.11 k/v,