When you create the extrude nurbs, you have the option of using ‘regular grid’ which will eliminate triangles.
Also, when the extrude nurbs is still in it’s original form, you can increase subdivison in the extrude nurbs object itself in either the rendered image, the editor view or both.
Not really underatnding what you mean about not berng able to apply texture to the caps though. You should be able to apply textures to anything.
Understand that when converting an extrude nurbs object to polygonal form, anywhere from 1 to five objects are created (extrusion, top and bottom cap, and top and bottom bevel). So maybe that information will help you somehow to understand your texture problem.
Post a pic if you can..It’s worth a thousand words as they say.