Is there a proper way to model to optimize performance?

I am using the Oculus with the UE and the frame rate sucks. I was wondering if there was a proper way to model things? I remember reading that it didn’t make a difference whether an object has 1500 triangles or 10 because the draw call cost was the same. Is this true? Also, does it make a difference whether each object has a bunch of elements or should I minimize the amount of elements per object? Should I join all the meshes that I can into one? In terms of copying and pasting, is it better to make a component or block in the 3d modeler or to make it in unreal? does it help to make things into components or is the render time the same?
Also, I just learned how to pack textures together as one so as to minimize the number of materials in the scene. what is the best resolution/size for this? If I use a very high res texture for one material mapped to different objects, is that better than just splitting them?

Any help is much appreciated.