Encryption SSL configs

Yes, you could have a virtual server listening with no clientssl profile, and it will just be passing anything that it receives from the client through to the pool member, so the pool member could certainly negotiate SSL with the client without the LTM being involved in the SSL at all.

The advantage of using a clientssl profile is that you can offload the cpu intensive work of encrypting the data to the hardware available in the BigIP, reducing the CPU load of your pool members