You will need to have a VS8F-3 in Slot A in order to install any PLUG IN programs and establish the KEY card, however if you turn off the VS8F-3 Sw and that VS8F-3 is still in Slot A, the V Studio will not recognize that there is any effects board in Slot B.
Because using the VS8F-3 disables tracks 15 and 16, it might be desirable to move your VS8F-3 KEY card to Slot B after the PLUGINs have been authorized and move your VS8F-2 back to Slot A. This would allow you to turn the VS8F-3 Use SW to Off whenever you want to have 16 tracks and still use VS8F-2 effects.
Because using the VS8F-3 disables tracks 15 and 16, it might be desirable to move your VS8F-3 KEY card to Slot B after the PLUGINs have been authorized and move your VS8F-2 back to Slot A. This would allow you to turn the VS8F-3 Use SW to Off whenever you want to have 16 tracks and still use VS8F-2 effects.