Reading the related documentation it is not clear what component manages the traffic and what cases this scenario covers. For example why install Istio if user will have Kourier enabled in Serving CR?

See customer case: https://access.redhat.com/support/cases/#/case/03419250
We should document in a separate section the current supported configurations (copying from the customer case):

Yes he can use Kourier together with istio, but keep in mind, that only one ingress controller will handle the ingress path, so he can either:
a) use Kourier only
b) use Kourier as ingress and istio as a Service Mesh (istio is not routing ingress traffic in this case)
c) use only Istio as ingress and Service Mesh

Story:
As a user in order to understand my networking options, I want to see diagrams showing the traffic flow (from external to the cluster eg. OCP route to kourier ingress, between internal services via the local gateway) for different configurations provided when istio or kourier is enabled.

cc rh-ee-rlehmann