You have the same general understanding that I do. AFAIK all 3D programs and renderers convert quads and n-gons to triangles in the end (even if behind the scenes, unseen to the user). For n-gons its a total guess as to how it will be converted (almost never ideal) and for quads there’s two options for converted to tris (either diagonal). Sometimes one diagonal is great and the other awful depending on the model. That’s why game artists are mindful of converting to triangles by hand.
All of this is especially important for lo-res situations. However as game technology advances and gets ever closer to eclipsing non-game tech, like supporting billions of polygons, triangles will likely get less and less consequential.
