Hi Dario,
generally reducing image quality doesn’t decrease CPU usage, but reducing frame rate does. It is possible to set any value from 1 to 1000 by editing manually the node.cfg file on server side. For example, to have 10 frames per second, you can uncomment and set the following keys:
DisplayServerVideoFrameRate 10
DisplayServerUseVideoFrameRate 1
Another thing you can do is disabling the “lossless refinement” algorithm:
DisplayServerExtraOptions “-refinement 0”