Hi,

Backgound

I have a single level 4 bedroom house, about 250 square meters. Currently I have a 100/20 Mbps Fibre Internet connection, an AC WiFi router and an AC WiFi range extender to minimise dead spots at the other end of the house. Overall this setup works well for fixed devices but roaming devices (phones, tablets) are a bit of a pain becasue they often hold onto the router wifi SSID too long and experience very slow speeds or drops instead of swapping to the wifi extender SSID. The number of connected devices is increasing (currently about 14 inc smart devices) and I'm upgrading to a 900/500 Mbps Fibre internet connection shortly so I'd like to upgrate the house WiFi to ensure all devices work seemlessly and have the best possible connection speed. 

Specifc questions regarding RE505X

1. If I keep my curent AC WiFi router and have the RE505X in bride/extender mode will it extend the AC WiFi or provide AX WiFI?
2. If I run some ethernet cabling to the centre of my house and have the RE505X in AP mode does it operate in AX mode?
3. Am I best to simply turn off the router WiFi and purchase a 2 pack Deco X60 mesh kit? 

Would appreciate any help or advice.