The speed between the Ethernet over powerline nodes is independent of the Ethernet connection of the devices connected to them.
You can see the link speed between the nodes in the TPlink app.
They also support LAG, I have two of the 3 ports LAGed to a Switch.
From what I can tell the biggest issue with these other than the wiring/noise issues is if people rely on them as a switch.
I used to have 3 devices connected to them (AP, TV and Xbox) switching to LAG and a proper 1gbe TPlink switch that ironically costs more than the homeplug more or less solved my issues but ymmv.
I also think that the UK residential power wiring that uses ring circuits might be better for homeplug usecases than other curicut types.
Oh, so you're talking about the speed the adapter tells you. In my experience those speeds are about 2x what you'd get in reality over a TCP connection (using something like iperf3).
If you have time, could you run iperf3 (brew/apt install iperf3) between two computers separated by the powerline devices?
I would say performance is so contingent on wiring quality that it cannot be reasonably assured. I tried out a TPLink system that claimed to be able to deliver 300 mb/sec and only managed 10. The fundamental problem is that you tend to want to place the units in areas with the highest potential for noise (eg near lots of electronics).
Your experience is typical even in the cleanest of AC power conditions. Powerline is hilariously oversold and regularly provides less than 25% of the advertised throughput.
The "2 gigabit" adapters top out at 470mbit when both sides are plugged into the same duplex receptacle. That number is cut in half when you move to another room, and it gets worse from there.
Every Powerline vendor, without exception, are using funny math when coming up with their advertised throughput numbers. In no situation will they ever be able to provide 50% of their stated throughput, and more typically it's closer to 10%.
