Hi Chaithya,
Welcome to GNU Radio community. From my experience, GSoC in this organization is a wonderful experience.
To get started, read
GSoC Information on Wiki if you haven't already. Also, I would suggest you go through all
tutorials on the official GNU Radio wiki. If you have the probable module you want to focus on then you can play around with them after the tutorials.
I am not sure about the query regarding the USRPs. But one of the best ways to understand the current structure is to solve some existing bugs and/or add a feature. Since you have a particular interest in some specific modules, you can try to solve relevant issues. According to my experience, solving 2 bugs will give you (almost) complete idea of the particular module. It may not be important for decision making (I don't know about that), but it will definitely help you to understand the community workflow and GR structure.
Meanwhile, once you get feel of how everything works, you can start thinking about the project, the scope, and workflow. Post your detailed thought on this thread for discussions.
All the best.