Will Adding More Homeplugs Reduce Speed?

I currently have a pair of TPLink AV500 homeplugs which perform OKish (65meg goes in one end, 20meg comes out the other two floor up). If I add more homeplugs around the house and thereby increase traffic over the wiring, will that reduce the speed coming out the original pair?

If any of the extra homeplugs are also wifi and G rated devices connect to it, will that drag down speed just at that homeplug or on the router's wifi as well or even across the whole network?

A lot will depend on the comms speed the plugs are connecting at between each other.

Generally mixing different HomePlug speed version is not a good idea, i.e stick to the AV500 ones throughput.

The WiFi side is different, but any G only devices will pull down the wireless speeds.

Thanks for the reply. Yes I understand not to mix and match plugs, read that many times. But I can't see anywhere if adding more plugs (and therefore more traffic) will reduce the output speed at the existing plug

The bandwidth between them is "shared", and the slowest device (e.g. the two furthest apart) will set the speed for them all.

If the link rate is negotiated down to about 20mbit already, adding one further away could well reduce it further, and if you try to use both for something at once, expect 10mbit from each.