It might be helpful if people that experience lag to post what algorithms are in each program you switching between? Maybe some algorithms are more difficult to get seamless? Maybe the presets have different routing and the dry path is being broken?
I notice lag going from a program with a reverb and delay in parallel to a pitch and delay in series. I find most of my programs that are just reverb and delay in parallel switch seamlessly.
I wouldn’t expect two completely different algorithms to not have some glitch when switching between them. And then if they also have different routing? I think there are some circumstances where expecting completely seamless switching might be unrealistic.