Yes! You can use multiple NCS devices to speed up inference. Are you using the NCSDK with the NCS1 or OpenVINO?
If you're using the NCSDK, there's a GoogLeNet sample in the ncappzoo that shows how to use more than one NCS (here). Another sample program you can look at is one made by an NCS community member, where he uses MobileNetSSD and multiple NCS devices to do object detection.
I hope this information is helpful!
I use OpenVINO with NCS2.
I have another question. Can I run two different network for two NCS2, such as a pose estimation algorithm on NCS2-a, and a face recognize algorithm on NCS2-b?
Do you mean running two different networks in one running application on two NCS2? Or do you mean running two NCS2 with different networks independently of each other?