not sure if this has been documented here, but....
clicking auxiliaries to external in stm1632 (so that the sends & returns show up in the routing window) will knock 2 notches off your dsp meter (well it does on my Pulsar 1 anyway)
I also noticed loading external effects intead of inserting them all into racks/mixer insert slots, saves some DSP and helps DSP stability. Last projects, I've been using Micromixers w MultiFx racks again. It seems to run cooler.
Hint for the MultiFx, to keep an oversight: assign midi channels to each rack according to the mixer channels they're connected to. So now you can quickly recall the right rack from the LiveBar.