@MkrtichBesides different power circuits it could also be the quality of the wiring in the house. The latest seem to be 2GB powerline speed or 1.3GBS powerline with 867MBs wifi (5GHZ) - TPlink.
I have been looking at these for my brothers place, but still trying to find the best as the walls are brick and the floors are concrete and it's a three story place with no CAT 5 or 6 cabling between the floors!!!!!
Yes agree , wiring condition does have an influence. Things have certainly moved fast since last I looked at Powerline Adapters 18 months ago. WiFi is now an optional feature and those TP-Link units appear to have leading operational credentials and the speeds you quoted are unexpectedly high. Powerline Adapter speeds are set by Marketing departments and usually don't take into account real world. With the AV500, I recall getting speeds of under 100 Mbps which was fine. Must do some reading on the newer technologies to catch up on knowledge.
Just realised I didn't paste the French Sagemcom URL in earlier post.
This site shows a lot of Sagemcom modem products - the fast-286-vodafone-super wifi is on Page 5 - it may not be the Optus version - it shares the same form factor - no user guide or specification sheet, just the Certificate PDF which provides part numbers which I have not been able to locate on the web.