YMMV but I seem to realize I’ve done quite a bit of fiddling with reducing CPU myself. I recall that with some VSTs or even KONTAKT instruments you can get higher CPU happening with the built in effects than with some external effects particularly reverbs and the like.
I recall turning off the internal reverb of a synth, and instead sending it in GP to a global rackspace that included the MeldaProduction MCharmverb VST. It seems to be very efficiently coded and I noticed a significant drop in CPU (although I can’t remember the details). This will probably vary a lot too with the parameters you need for the reverb sound you want.
I guess it wouldn’t take long to try this tweak, turning down/off internal effects in a VST and finding out if this efficient reverb (for example) instead will first of all sound as good and second; reduce your CPU utilization. Might be worth a try.
Also it’s very tempting to pick the “high quality” options in VSTs but really a lot of people just cannot hear much above 15kHz even lower if the speakers even reproduce it, and you’ll find most people CANNOT hear a difference between these higher quality settings which can use a lot more CPU.
This is one of the awesome things about Gig Performer - you can just “whip up” a test rackspace to find out the answer to something like this. Go whole hog and just open a blank .gig file and save it as “junk” and find out. If it works great you can export that rackspace and import it into your show gig file!