Hello Tobias,
Thank you for reaching out to us.
To clear up what an SBSAR (or Substance Archive) is, here is a excerpt from the Substance Designer documentation - original page available
here:
Substance Archives are compiled, optimized Substance files. They are much faster to calculate and can easily be shared without reference issues. Parameters can still be tweaked, but editing the graph is locked down. Substance Archives can be used in all Substance applications and any application that has a Substance Integration (some with an external plugin) such as Autodesk 3DS Max & Maya, Unreal Engine 4 or Unity Engine.
Indeed, the default working file format in Substance Designer is SBS (Substance File or Package). You can create and work in graphs contained within a package. Please note that you can place instance nodes of SBSAR files in a graph.
To get comfortable in Substance Designer, we recommend checking out the learning resources available in
Substance Academy.
We hope this was both helpful and informative. Feel free to get back to us if you need further assistance.
Have fun using the Substance tools!
Best regards,
Luca Giarrizzo