during modelling, quads are better for most areas, but before baking normal maps, you should convert those quads to triangles, and make sure all the triangles flow in the proper direction to create the correct silhouette. if you bake a normal map with just quads, and export the FBX as quads, UE4 may turn some of those triangles the wrong way on import, distorting your normal map, and ruining your silhouette.
if you are using 3DS Max, you can turn the invisible edges without converting them to triangles, but many other packages, including Maya and Blender, do not have this feature, and require you to cut some quads into triangles to make sure they flow properly. either way, on export, it should be triangulated, so UE4 doesn’t have to guess.
rigging a model that is triangulated is no different from rigging a model made of quads, as long as the vertices are in the same place, it will be the same process, with the same result.