I have quite many widgets here, trying to run on a MacBook Pro (Retina, 15-inch, Mid 2015) with MacOS 10.14.6 in Ableton Live 9.
With plugin GUI window open I get 15% CPU, while this goes down to 2% when the window is closed. Of course plugin running in standby in both cases.
It seems that the openGL does something - I notice some red background blink when resizing and some deformed circles. Btw. only for the tiny ones, e.g.
image bounds(136, 94, 5, 5), shape("cicrle")
But it doesn’t seem to make a change on the CPU meter in Live. Do you have any clue or additional info?