Thanks for all your replies, folks!
I find the plugin behavior a bit odd, because it also makes the entire Cakewalk UI very unresponsive. Seems to make no difference if the plugin UI is visible or not. The UI of the plugin is also very stiff, it takes a long time to see any alteration in the settings.
My soundcard is Focusrite 2i2 (1st gen), with the latest drivers, on Windows 10 1803. I might to tinker with buffer sizes as well to see if it makes any difference. I think the setting was 1024 samples, as high as it would go.
Have to try the plugin on a small project by itself to see, how it is then...