So I just installed Mojave on a MBP 6,2 (mid 2010 with Nvidia Geforce 320M maxed out RAM and SSD) and I am getting pretty bad Quicktime performance when playing back 1080p files that played butter smooth under HighSierra. I see that others have had Quicktime Issues but not with my exact model. Anyone have any solutions to improve quicktime performance?
Did you try the GVA patch posted earlier in this thread? It fixes several graphic speed issues on the older Nvidia based laptops. Worth a quick try.