At the moment every single "next generation" project is per default an "open" project. Everybody who has access on jira can see and edit this project. How can i avoid for example external user can see every single next gen project? External means members of an external company who has access to jira, but should only see projects they are relating to them.
Yes an admin could change the project permission for every single one to private but this take too much time.
For the old projects you could use a permission schema per default to avoid this behavior.