static route versus IP forwarding VS

0.0.0.0/0 VS (PerfL4-type) actually is the best solution to establish internet connectivity for the back-end servers via F5 in your case. Static routes only define the next hop to reach a destination, but they do not effectively cause a routing to take place. They are useful as supplementary exceptions to default route.

I'll post the config I use in 99% of cases.

1. It consists of a custom FastL4 profile to make F5 a non-intrusive middleman (behave like a router)
2. A pool which has either one or more default gateways to reach Internet,
3. And a very broad 0.0.0.0/0 Virtual Server which listens on internal (server-side) VLANs that should have Internet connectivity via F5. This VS will only get a connection if there's no closer match available.

conf:

ltm profile fastl4 pr_fastl4_stateless {
    app-service none
    defaults-from fastL4
    loose-close enabled
    loose-initialization enabled
    reset-on-timeout disabled
}

ltm pool pool_default_gw {
    members {
        172.16.0.1:any {
            address 172.16.0.1
            session monitor-enabled
        }
    }
    monitor gateway_icmp
}

ltm virtual vs_0.0.0.0_any {
    destination 0.0.0.0:any
    mask any
    pool pool_default_gw
    profiles {
        pr_fastl4_stateless { }
    }
    source 0.0.0.0/0
    translate-port disabled
    vlans {
        vlan_server_side_2010
    }
    vlans-enabled
    vs-index 4
}