Choosing the proper role
Guest
Have the least rights. This is recommended for people you ask for consultancy.
Developers
The choice for most people you want to invite to your ARC. Developers have read and write access, but cannot maintain the project on the DataHUB, e.g. inviting others.
Maintainers
Gives the person the same rights as you have (except of removing you from your own project). This is recommended for inviting PIs or group leaders allowing them to add their group members for data upload or analysis to the project as well.
A detailed list of all permissions for the individual roles can be found here