Finally taking some time to dig a bit deeper into the Engine COMP.
I observed, maybe related slightly to your points, that when setting the engine comp to Synchronized clock my main process is dropping frames (slightly, but still).
Strangely running the content of the engine COMP in the same process doesn’t cause frames to drop.
Not sure I understand why… would all the back end logic related to syncing clock take much resources ? It’s odd.
EDIT: I posted here some of the things I noticed 2020.25380 - Engine COMP frame-rate and performances issues