Can I add tl-wpa8631p to PLC network of tl-pa9020p?

  Hello @JWikoff 

TP-Link powerline devices are compatible with each other, it possible it is recommend to select model of same powerline speed, like AV2000 + AV2000 kit.

Here is guide that help select the powerline devices: 

How can I select the powerline device?

  @Solla-topee  Is there a wifi PLC model faster than the 8631? I didnt see one in the current list.

 Hello  @JWikoff 

In the U.S. the fastest wireless powerline model  is AV1300 ( TL-WPA8630(P)/TL-WPA8631P)

https://www.tp-link.com/us/home-networking/powerline/

For AV2000,  it is recommend to consider AV1000 like TP-WPA7510 as the above FAQ.