Live view is the fps of the BI interface. Lowering it can have a large effect on cpu. Setting it to 15, or even 10 should still give you smooth viewing. With that many cameras, you may need to go to 5?
UI3 is awesome, I agree. And, i use it from time to time remotely to view and change BI settings. But, logging in remotely will always increase cpu by a factor of (cameras*quality)*cpu... or something like that.
Ti simply view the cameras when I'm away from the BI server, I use an android app called 'IP Cam Viewer' by Robert Chou, to view the cameras remotely. It logs into the cameras directly, and gives full control of the cameras. All camera settings are retained in the cameras, and by default, BI.