It's built of triangles so a quad is 2 triangles etc.
The advice about using quads I'm not sure is really a tautology. I tend to work with quads until one of the quads is non-planar then I cut it so that when I bring it into a game engine the import/bake step doesn't triangulate the mesh in a way I didn't want it to.
opengl can do dots, lines, triangles, quads, ngons. just an option in the drawcall. pretty sure dx and vulkan will be the same but i didnt try em... what is more optimal.. idk.
maybe under the hood past the drawcall it will triangulate it. never bothered to look into that.
pretty sure the HW doesnt care one bit as it operates on vertices... not primitive shapes. (ofc like u note if ur quad is non planar it wont look like u expect but thats no concern for the driver or hw..)
I though about mentioning that but I didn't want to muddy the waters. There other option in opengl like you said but I can count on one had the times I've used them in a professional context and I think possibly zero for anything that I've shipped. Also I have never looked into what it does under the hood in those cases. You might be right.
The advice about using quads I'm not sure is really a tautology. I tend to work with quads until one of the quads is non-planar then I cut it so that when I bring it into a game engine the import/bake step doesn't triangulate the mesh in a way I didn't want it to.