I have a setup two appliance in cluster and defined 1 VIP on Loadbalancer and It works perfectly.
Just to note CA PAM appliance works in Active/Active configuration not the Active/Sandby, You will have both appliance ready to receive user request at a same time. Load balancer will play a vital role of distributing traffic among both appliance. Just double check the Load balancing method you wish to configure, I recommend using round robin with sticky client IP address.
For your question regarding VIP on PAM , I think it is used for internal communication , Don't think that will do load balancing of User traffic---Eager to see reply from support or development team on this point.