I’ve gotten it to work just fine across my LAN and over the internet through my firewall.
From what you’ve written I understand that connecting to a Raspberry device, everything is working well. But when connecting from a Raspberry device or smartphone with the NoMachine mobile app to your Windows 10, you cannot see applications windows. You see only the desktop. Right?
On my Windows 10 Machine it seems to work fine except none of the windows display remotely.
What applications are actually running there? I mean, if I was physically in front of the Windows PC , what applications would be open?
Is the Windows PC with multi-monitors? If so, take a look at this tutorial: https://www.nomachine.com/switching-the-view-between-multi-monitors-during-a-remote-desktop-session.