Thank you for your guidance. I think I’ve got the general idea. When poles appear at corners, the corresponding arcs will be larger. Conversely, adding supporting geometry shifts the poles to other positions to achieve tighter arcs. The exact location of the poles is not critical. What matters most is whether the light and…
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.
Frankpolygon's perspective is what I'd think about plus the principles discussed relate too other shapes/subd processes as well e.g. Hemispherical intersections "Segment matching is a fundamental element of most subdivision modeling workflows." It's not the topology "A significant problem with trying to formulate a fixed…