It doesn't work that way. If you use 500m and 200m adapters the whole network will run at the slower speed. With just 1 pair of network adapters running at 200 you would get about 50m of actual usable throughput. Running 3 will drop this down to about 30m total but it greatly depends on the traffic. The problem with 3 adapter networks is they form a direct connection between the 2 pc even though you might not actually have traffic between them.
Plugging 2 adapters into the router meaning you are now running 2 pair will likely work worse. The 2 pair of devices will assume they can each use the electrical wires and stomp all over each other. Now if you were to use the same key/password the 2 units connected to the router would...