Hi! Sorry for the late response 
1 A) - The current implementation is for the Omnichannel. So guest’s messages from Whatsapp will create a new omnichannel room/chat, not on a channel. However
B) multiple agents can interact with this visitor.
B) 2 - Yes, you can initiate the interaction using the templated messages.
B) 3 - This integration has official support from Rocket.Chat.
B) 4 - This integration works only for direct messages
B) 5 - I will have to check for this answer.
I just published an announcement about this new integration, please, feel free to interact or post any other doubt there. THanks!!!
https://forums.rocket.chat/t/new-whatsapp-integration-available-for-all-community-workspaces/12841/2