There are 3 things i would do:
- switch off “load on demand” under options
- set “midi only” in the mixer
- load a predefined externalVstiKit like “addictive drums->ad jamsitx”. These kits are set to midi only
Peaks can happen here too, while jamstix is (re)creating parts. But never with dropouts.
further:
you can create indivdual things/mappings with the input-transformer within cubase and save these tracks (together with your drum-vsti) as a track-preset. This makes things much easier 
… and you are right. It has a learning curve. I mentioned that earlier. Best advice i can give you: go slow. Try basic things like powervalue, drummer exchange. Dont invest time in the dropdowns to early. They are mostly advanced, but powerful.
btw. what is the demo missing? I never tried it.
Have fun