Yes, FBS works on the offer level. This means that you can list a product with 2 offers: one of which is FBS, another is fulfilled by you.
Operational & Safety Guidelines at Souq Fulfillment Centers
Souq Fulfillment Centers : Locations and Contact information
What is Fulfilled by Souq (FBS)?
Listing and Creating FBS Shipping Notices
How can I register with Fulfilled By Souq?
Can I request to recall my Fulfilled by Souq products from your fulfillment centers?