Maybe some confusing phrasing, custom collision and collision according to mesh name are the same.
You have 3 options:
- If you do not tick the Import Collisions: no collisions will be imported or generated
- If you tick import Collision but not Import Collisions According to Mesh Name then UE generates collision for all your meshes based on fallback collision type
- If you tick both import Collision and Import Collisions According to Mesh Name then UE will use the UBX_ UCP_ USP_ UCX_ as collision meshes for corresponding meshes. For meshes that do not have a corresponding custom collision then UE generates collision based on fallback collision type