It would be a great feature if MasterPlan could idle when not visible. I
I got MasterPlan back in January. I have used the most recent version in the past few days v0.6.0 (version 3 on the download page). I run it fullscreen on a 2018 Macbook Pro, but it is not visible most of the time as I work with apps on other workspaces. I have configured MasterPlan to 30 fps, but it continuously consumes 10-27% CPU.
( I think there are events for occlusion in the Cocoa framework https://gist.github.com/zwaldowski/8710fddc8b0b39d2c152#10_9Occlusion)