Provided that the server is indeed set up correctly (so in this case it’s Windows with a supported Nvenc-enabled driver installed) NoMachine’s use of HW acceleration for encoding works out of the box.
So we should assume that the problem is client side, with decoding. Looking at the screenshots it appears the resolution of the remote display is higher than 1920×1080.
Are you connecting from a Windows client? I ask because when connecting from Windows, NoMachine can support remote display resolutions up to 1920×1080 and not beyond.
More about this is available here: https://www.nomachine.com/AR09L00811
If you’re not connecting from Windows, then we need to investigate further.