The model for the primary detector (/opt/nvidia/deepstream/deepstream-6.3/samples/models/Primary_Detector/resnet10.caffemodel) is a “a DetectNet_v2 model with Resnet10 as backbone”, There are some discussion on this topic Resnet10 “primary detector” - Intelligent Video Analytics / DeepStream SDK - NVIDIA Developer Forums.
The several sgie used in deepstream-test2 (Secondary_CarColor/Secondary_CarMake/Secondary_VehicleTypes) are all for classification.