ivsEdits requirements are higher than other NLEs because it supporting LIVE features it is always in Play. Also if the timeline is empty it is sending with same projects settings a sequence of blackframes to the outputs with same rate and resolution of the project. Moreover to manage RGB 4:4:4:4 /32 bit it is more hard to manage mixing in YUV mode.
What is your project rate and resolution? What is your CPU model and frequency?
Best regards
Roberto Castellano