Couple of thoughts after installing a 2 unit Velop setup. Wasn't as quick as I had hoped, but part of that was my fault. First, if you're planning to use ethernet on node 2 as the backhaul, it has to be wired directly to node 1. Ie. not through a router or hub. I'm not a network pro, so this was not obvious to me. (Even though it was mentioned how Velop NATs everything.)
On top of that, when installing my Devialet Phantom Gold speakers through the Dialog box, they didn't work. Again, NAT stuff. (The Dialog could not sense the speakers.) After talking to support (which were very helpful), I moved the ethernet cable to the Dialog from a hub to Node 1. Then it worked. Of course, now I can't use ethernet for the backhaul. Great.
Luckily, the nodes see each other and the wifi backhaul seems to work great. I now have great wifi coverage and speed in my whole house. After years of trusted service, I've turned off my Apple Airport Extreme.