Check how it looks when materials are applied, and it’s put in a scene with lighting and camera angle. Many of these tiny issues become essentially invisible, in situ. But yes, triangles and ngons are ok, as long as they don’t adversely affect the shading. Usually fine on flatter areas.
@zylan Determining if a high poly mesh is acceptable really boils down to how closely the shapes in the model match the shapes in the references and whether or not the topology subdivides cleanly, without generating any noticeable smoothing artifacts or other surface quality issues. If the shapes and surface quality checks…