I would recommend you install and test the plug-in to be sure, since hardware configurations often differ and can potentially change the behaviour.

I just did a quick test on my laptop pc, and capturing from 2 displays with animated content I am using ~70% LOAD in Isadora at 60fps. This tells me I could do much more before I am mxed out since the GPU isn't working very hard. It all depends on what I want to combine.