So you would like to pass all device groups of the device to the transport and then use event rules to route the alert? In my case creating multiple PD services and managing the alert rules and transports in NMS worked fine. Some devices would alert to different transports depending on the physical location or role of the device in the network. Then in PD you can create custom logic with escalation rules to alert certain group of people and escalate the alert.
Simple install flow has not worked in a while and would probably need a support ticket to be activated again. But it does not differ from using the API keys at all - just create the integration endpoint in the PD, select LibreNMS and copy paste the key. Using or not using simple install flow does not affect the transport itself.