Hi,
welcome to the forums 🙂
To answer your questions:
1) To connect with NoMachine you need one of the NoMachine servers installed on each machine you want to access. So, let’s take the Free Edition as an example. Download and install NoMachine FE for Windows on your Windows computer. Then download and install the Free Edition on your Ubuntu machine. The operating system can be physical or virtual, it doesn’t matter, but there must be a desktop environment installed there.
Then, on the device you are connecting from, you can install either the Free Edition or Enterprise Client. All NoMachine server packages contain both the Player and the Server components. The Player is what you need to be able to start a connection. The Enterprise Client package contains only the Player.
NoMachine’s model is “number of connections per server” and they are counted on the server, not on the device you are connecting from. See the following articles for more information:
https://kb.nomachine.com/AR07L00808
https://kb.nomachine.com/AR10K00716
2) To access any VM, a NoMachine server must be installed on each of them.
Take a look at the following article: https://kb.nomachine.com/AR11E00489