No, a VSD group is not necessary. VSD-0 gets created automatically when clustering is enabled. You just need to tweak the priority values on individual boxes.
There is no 'seperate' manage-ip for NSRP. It is the same as interface manage-ip. When 2 devices become a part of the cluster, the Master FW becomes the owner of the inteface IP, leaving the backup unmanageable via inband options.
Adding a dedicated manage-ip to each device will ensure that you can manage both of them individually.
Note: This thread is already marked as Solved and might not get the attention of all Forum users. If you have more queries, I suggest you create a new thread.