modeled all the parts and just "stoked" to some objects in the other creating the illusion of integrity
So it is possible, better to save on polygons, but this approach is fraught with problems with rendering z-buffer, for example https://sites.google.com/site/threejstuts/home/pol...
But if the programmer (game, project, or whoever the model in a 3D engine will insert) will be allowed, and so, too, is a "correct" approach.
still have to use triangle ... or should all the outputs on the 4 corners?
Tell you a secret - when you export any 3D model into triangles. A rectangular polygon is nothing like two triangles. Five corners - three triangles, etc. And when you consider the number of polygon, usually mean the number of triangles exactly (face or trisul, faces / triangles). 3D game engines only with triangles and work. And even better some where manually the polygons into triangles to break up, to curved surfaces to the right diagonal crossed rectangle.
The square polygons are very necessary if the model (skeleton/mesh) after smoothed subdivi (subdivisions) or in the case of 3D max - massmoca/Turbomeca (meshsmooth/turbosmooth), because the triangular polygon is not uniform cause some "tension" smoothing on the frame.