Rasterization engine performance is affected mostly by triangle counts. Ray tracing is affected mostly by output resolution.
A hardware bounding volume hierarchy (BVH) is built for each mesh. BVH's are used for intersecting rays with meshes. A BVH has a location represented by an AABB. Rays are checked against every AABB the ray passes through until a mesh surface is hit. The fewer BVH's a ray is checked against, the faster the scene. In areas where the player is, be conscious of where rays can pass through one ore more AABB's without hitting a mesh surface. Divide big meshes into smaller meshes when modeling to reduce open space in the AABB. Avoid the player being inside a mesh AABB. Scene performance will benefit whenever it's possible to use these techniques.