You don´t necessarily need to set the laency compensation, youu can also use synchronous Processing (it needs more CPU, though).
Plugin´s latency is checked on startup of the host. The Vienna Ensemble is an application outside of the host, connected via VST. As it starts AFTER the host, you need to manually set the latency (once, if you don´t change the buffer settings of your soundcard). There´s no other way to do it, technically.
So if I understand correctly, when manually set, The Vienna Ensemble Engine doesn't worry about the host latency, and if Synchronous processing is checked it "read" the latency when it starts then doesn't dynamicaly change this latency if you choose to change the host latency. So I don't understand why it use more Cpu.
btw : Is the cpu needs for Synchronous Processing relative to the polyphony ? Fixed ?
One last question :
When you use Vienna Ensemble on a slave computer with Fx-Teleport, which latency is the correct one ? Host latency ? FXT latency ?