Wait, what about NLU. There are some prebuild integration.
wit.ai from facebook
api.ai from google
Nodes contains ms-luis
big pack for IBM watson includes NLU
You want hot-word activation?
Snowboy it is.
moni.ai can make it, too.
Now. you have one chatflow clone with flow from node-red. NLU from facebook/google/ibm. with lots available node at https://flows.nodered.org/.
At the end you have to know. Node-red is single processed flow environment. If you want to run many flows, pick a docker/service management to do it, or use something like FRED, depends on what you need.