Hello. I dont know if exist a demo preset but my personal experience is that it depends on what your actual needs are. What do you need to do? Which is your pc specs? From my personal experience you need to know your actual needs.
As general rules this https://www.vmix.com/sof....aspx#systemrequirements is true at some point. I have i7 10th gen and gpu quadro p4000 (same architecture like 10x series but i see is more stable) but i tried also the 1060 and 1050. It is true that we can have 4 cameras and 1 streaming and 1 recording. But if you combine the cameras with some graphics and virtualsets then you may have gpu overload and problem
You can overload your specs by adding inputs in vmix and try to do tests. For example if you input 3-4 4k videos and play them same time a middle range consumer cpu will go 100%. But in your real workflow will you need to do this? Or try replay or multicorder etc. But you need to have your cameras,either sdi/hdmi or ndi/srt. So my opinion is try yourself and see
If it is for pc that you want to buy,you can ask here in https://forums.vmix.com/topics/7-Systems and see other users experience for same hw like yours. Or also there exist 2-3 fb groups for vmix and also reddit vmix community that you can ask for your hw by describing what you need to do. Or also vmix support