I do notice that there a lots of WiFi networks visible where I live. When upstairs some of the other networks appear to be more powerful than my own network even though the houses are all detached and spaced apart so i'd have expected mine to be more powerful.
Yes, different makes of router can achieve more transmission, depending on the design. Most of the ISP provided routers are quite cheap, some of the third party ones can achieve more.
I live in a block of flats where 2.4 GHz WiFi is unusable due to the volume of people using it. Before lockdown it was okay, as most people were not at home - you could see network names, but they were not in use. Now they are in use, throughput on my 2.4 GHz has dropped to 50 Mbps with lots of stalling. On 5 GHz there is a lot less range, so I can get coverage of my flat, and I mostly get the full 200 Mbps of my connection.
I have Hive which also uses the Zigbe system, and I've not had any problems with that. If you have interference across all those bands, it make me wonder if you are a) near an airport, or b) near anything military? Wide band RF interference is very rare and you may need a guru, or talk to Ofcom ??
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