Currently, I think “Create and Edit (Full)” and “Can edit” permission level is so powerful.
Users which are granted one of those permission level of an item can COPY / MOVE / RENAME / ARCHIVE / DELETE a Project or a Task list. Those permissions should be exclusive for item owners, admins or team owner.
Imagine Project or Task list is a permanent structure in your company. You are the owner of your company. You hire (invite) employees to work in your company. Commonly, you will not allow them to change that structure, or else they will make a mess with those permissions. They should only have the permission to create / edit tasks in their own departments. Everything else related to company structure should be responsibilities of the managers or boss (item owner / admin / team owner).
Futhermore, similarly with permission in tasks, item owners / admins / team owner should be exclusive users who have permission to Delete / Merge / Convert to subtask / Archive a task.
Ultimately, my point is all changes affecting to properties of an item should be exclusive to item owners / admin / team owner.