Model: x20 (1 as main deco, 2 as nodes)

wifi: 500mbps

2 storey house with 4 bedrooms 

Speedtest via deco app: 500mbps

Speedtest via phone (in front of deco): 20+mbps

I am unable to resolve the low WiFi speed issue on x20 and planning to get other deco model to replace it.
is there any recommendations for deco with good range & WiFi speed?