GTM sync group and prober pool

1. I'm not 100% sure on this but I think simply running gtm_add on a new gtm to join an existing sync group will result in all the gtms trusting each other. Shouldn't need to run on every gtm.
2. I assume when you say "probe" you are referring to health monitors and not LDNS probes (they are very different). By default the monitors are always run by a bigip in the local DC. In other words your LA gtms would NOT be monitoring the NYC ltms and vice-versa. Prober pool does allow you to select which bigips do the monitoring in a DC so if you would like to have some control over it do that but shouldn't be necessary.

Scott