In OptiX 6 and newer the BVH traversal will always use the RT core hardware on RTX boards.
The additional hardware triangle intersection is used for the built-in triangles primitives only.
These do not have a developer-defined bounding box or intersection program as they are built-in.
Only custom geometric primitives have developer-defined bounding box and intersection programs.
The bounding box program is only called during acceleration structure builds, the intersection program is called during the BVH traversal when the ray is hitting an AABB.
OptiX 7 doesn’t have bounding box programs at all. It’s your responsibility to calculate the AABB input for custom primitives, normally with a native CUDA kernel for performance reasons.
OptiX 6: https://raytracing-docs.nvidia.com/optix6/guide_6_5/index.html#host#triangles
OptiX 7: https://raytracing-docs.nvidia.com/optix7/guide/index.html#acceleration_structures#primitive-build-inputs
Please read the OptiX programming guides and these threads:
https://forums.developer.nvidia.com/t/enable-rtx-mode-in-optix-7-0/122620
https://forums.developer.nvidia.com/t/optix-6-5-wireframe-rendering/119619/10