I am running Cubase 6.0 on High Sierra. My main issue is that the Activity Monitor is showing between 50 -100% CPU for cubase when on Yosemite it was showing a third of that. If the mac gets too hot, Cubase crashes. The fan is also more annoying on High Sierra.
I guess that Cubase 7.5 could be a bit like Cubase 6.0 on High Sierra.