With the assumption that the Loadbalanced and Standalone WANs are separate (and pointing to separate LANs) I would have two sets of rules, if for nothing more than long-term sanity -- it's easier to troubleshoot when something goes sideways if you've got a focus point (i.e. the different ruleset names).
set 1 -> "WAN_IN" for the loadbalanced WAN. This can be applied to all WAN interfaces that're part of the loadbalancer.
set 2 -> "OTHERWAN_IN" for the standalone WAN connection.
But then again -- that's me. If you want to just toss everything into "WAN_IN" and call it a day ... it'll work too.