Define VM Network for Virtual F5

No.....Yes.....
depend on your local routing environment - and what you are trying to accomplish.

I have HA pairs of  f5's with multiple DMZ vlans into 1 interface, and on the same box have multiple vlans providing layer 2 adjacency on a 2nd interface - with mgmt on a 3rd interface.

So long as vmware interface that is presented to the f5 instance, matchs the vlans per interface you are good.

if you dont need layer 2 adjacency - and normal routing allows access to the backends - you might not need the extra vlans on the f5 and or vmware.