@Acho 

Acho wrote

The Archer AX20 and Archer C4000 seem to be the same device. The C4000 being the Costco version.

No, they are NOT the same. AX20 is Wifi-6 and the C4000 is Wifi-5 (not an AX speed router).

The C4000 is similar to the Archer A20 though in spec's, see https://community.tp-link.com/us/home/forum/topic/167246

Can't comment on Mesh, but I doubt it would be put on the C4000.

@Acho 

The AX20 will get the OneMesh firmware, but it doesn't look like it for the C4000.

To see what is currently being worked on or planned, you can see our OneMesh section here: https://www.tp-link.com/us/onemesh/product-list/