Can a graphics card on the server increase performance using NX 3.5.0
No improvement can be obtained through more powerful graphics hardware on the server side. By nature, NX 3.5.0 doesn't use graphics hardware on the server at all.
Graphics operations are intercepted and translated in messages sent through the network. For example, with 3D applications, data sent over the network through the NX link, is the data produced by the NX agent when handling the drawing operation produced by GLX Mesa; it is not GLX traffic but X core protocol data.
If you want to benefit from graphics hardware on the server side, VirtualGL could be a solution.
It should work with NX 3.5.0 because it just needs to connect to an X server (and the NX agent is an X server). No special setting should be required of NX; just run the 3D application under VirtualGL in raw mode.
Users adopting the OpenGL application can use GLX extension, but only indirect rendering is actually used. The OpenGL functions are implemented in software by the Mesa library and no hardware acceleration is performed. You can read more about this here:
https://www.nomachine.com/AR09C00278.
For NoMachine 4 users
Please read here to know how to enable VirtualGL support in NoMachine 4: