Topology based Question

Topology will require multiple pools. It's configured at the wide IP level and will use records to determine which pool to balance to.

For the sake of example, let's say you took your pool with three members and split it into three pools each with one member. You could then build topology records to balance requests from certain countries/regions/etc. to your pools as you describe. In the event that the GTM has an equal score for two or more pools from a topology perspective, the GTM should round robin across those pools.

Regardless of which load balancing method you use, the pool and its members will have to be active before any client requests will be resolved to them (unless you aren't health checking the pools/members).