I have two 24" Cinema displays (Aluminum, oled versions) and both set to 1920x1200). Even if I drag scope in a asmall box over a nodes tab so Resolve use only one GUI monitor, is the same. I have been working on a single monitor system, with newer 2010 MacPro and it was working fine... I will try this suggestion for better playback performance:
but still it would be nice to have an option to not update scopes in playback. On laptop, when I take Resolve on set, there is a similar performance issue.