These companies are relatively unknown compared to companies like Lenovo, Dell, HP, etc. My guess as a layman would be that that Lenovo is not likely to try and "compromise" the hardware it sells (e.g. with additional chips that are meant to "phone home", or otherwise store data in some retrievable way) because that would damage their reputation and hence their business.
But a relatively unknown vendor might not have such a concern?
So I wonder:
* are my concerns even realistic?
* if so: how does one evaluate security risks that exist when buying PCs from "relatively unknown" vendors?