I have reviewed the material covered during my sophomore year and although it does not seem like a joke freshman year was, it shouldn't be very challenging either, it includes introductions to modern physics and waves with 2 labs and mathematically linear algebra, diffyq and vector calc. If I had more than enough spare time I would like to cover some extra areas of physics/math that had sparked my interest for a while. I thought about learning some quantum mechanics using Griffin's textbook and relativity using Hartle's book. I am pretty sure I want to continue with physics until I get out of grad school and I have read a lot and would be interested in pursuing cosmology, string theory and particle theory in the future so I thought getting an early start on topics/books mentioned would not hurt. I would welcome any suggestions if there any better options and how to go about self-study in terms of watching videos, reading, doing problems, looking up references to concepts that spark more interest.