OCP 4 Router Sharding

Im looking for info regarding router sharding for a OCP DMZ environment and found: https://access.redhat.com/solutions/3880621
And I am a bit unsure about the specifics, I got a new vmware cluster up and running.

I would like to create a router-external ingresscontroller that serves only routes that are labeled type=public or similar.

If I understand everything correctly, labels are used on the ingresscontroller to place the different router instances on different worker nodes?

If my default/internal router is running on 3 infra worker nodes and an internal LB forwards to these infra workers, I guess I need to place router-external on the other non infra workers.
And point the external LB to these workers, would that be the correct design?

EDIT: so to clarify what Im after a bit.
I think I may need at least 3 router shards in the end.
Preferably I want to run these on infra nodes.
Is the recommended design that I create 6 infra nodes to run these (2 replicas per router)...and add 2 more infra nodes if another shard is needed.
Or is there a way to configure which port the routers are listening on and run multiple routers per infra node?