核心要点 (BLUF)： Unwrapping is needed for texture painting and proper UV export; the atlas preview renders right into the task result.
A GLB model with the new unwrap and a UV atlas preview. With baking enabled, existing color/metallic/roughness maps are re-projected onto the new layout.
The limit is 80 000 equivalent triangles: bigger models are accepted at creation, but the task fails with a refund — reduce the model with Retopology first.
Retopologize first, then unwrap the reduced model: that order is cheapest and fails safe.
It is a quick render of the UV layout so you can check seams without opening a 3D editor.