SUT and Projects are different and separate notions in XStudio.
A System Under Test (SUT) must be seen as a release of a Product - (e.g. MyApp V1.2). You access it using the SUT module.
A Project is set of tasks and activities that are realized through Sprints. They are managed using the Project Module.
You group SUT together in Folders. There are different way to organize your product and release.
For example you could gather all of your products for one domain (e.g. BI) in one folder.
Folder = "BI Meta-release 2017-02"
Products (inside this folder)
- "Sales Analysis Dashboard v3.4"
- "Customer segmentation v1.3"
And you can then create another Folder for the Meta-Release in 2017-04 by duplicating this one and so on
This is to be used if your products have high adherence in between each other. This allows to rapidly control and report the sanity of your Meta Release.
Another way of managing can be to have one folder per product and in each releases of the product. This second approach is used if you have more independent products and wishes to the product as one continuum.
Note that you can also take advantage of the "company" notion in the SUT tree. For example you can organize you IT domains as several so-called "companies" - E.g. R&D, Production, IT & MIS, Partners ... each having their sub-domains (managed as Folders) and so on.
All of this also depends heavily on your release management and test management strategy. XStudio does not enforce any good or bad practices or organizations here.
Managing users and teams
When it comes to manage which users can work on which products, you use the User Module. This one allows you to create team and associate users to these teams.
Access Rights are managed by team. Hence you can state which teams have access to which Folders in each type (SUT, Requirements, Specification...).
Users have profile, which , combined with the access rights of the teams they belong to, will grant or restrict them with the ability to do action of specific objects. See Managing users' profiles and team's access rights