If you want flexibility and a closed chat then you may want to look at setting up a chat server.

Discord or similar, allow you to upload files into one location, you can set up chat groups for patrols, sixes or teams.

Make sure you are using private servers and you have control of who is invited to the chat and password as well as an invite helps make sure you do not get any uninvited guests.

(Discord does have a video option but it is a bit clunky and quality isn’t always great.)