A simpler way,
1. Perform 3D reconstruction like this video first and save the scanned result as OBJ.
2. Reload the OBJ into you scene.
3. Through SRWorks Unity API, ex: GetAllHorizontal(Vertical) / GetLargestHorizontal(Vertical) / GetColliderWithProperties( property array ), to get your desired collider property for your virtual object placement.
4. Or, you could even perform 3D Semantic Segmentation like this video to find wall or floor. A Sample code provided in Experience_Unity > Assets > ViveSR_Experience > Scenes\Sample9 – Semantic Segmentation.