As far as Mint goes, whether you choose Mate or Cinnamon will depend on how "current" your hardware is. For older machines I'd recommend Mate, for newer machines (with more resources available) I'd use Cinnamon.
However, both will run fine on a wide range of hardware, so don't get too bogged down in making a choice, just jump straight in.
As for VM or Live USB, both have their plusses and minuses. The advantage of a VM is that it is hardware independent, so therefore any OS will run in it.
The advantage of a Live USB is exactly the opposite, in that you can test any of the OSs that your interested in on your own hardware without needing to make any material changes to your machine.