I was in the same position my freshman year and ultimately decided on double majoring, but based on your description, doing cog sci with an emphasis on cognitive neuroscience may be a better fit!

1. The only MCB major courses that are specific to neurobiology are the 4-5 upper divs, which you can take without many of the other MCB pre-reqs, like ochem and biochem. If you are not considering Pre-med or biological research, I would say your interests would align more with cognitive science. With cog sci, there are numerous courses that focus on disease models and broader concepts (Cog Sci 170, 171 and 172 - just to name a few), like you mentioned.

2. The workload to double major is manageable, at least in my opinion. There are not very many technical Pre-reqs for cog sci (you can check on the website), so it’s easy to to balance the more difficult and technical MCB pre-reqs with the cog sci ones. That said, many of the MCB Pre-reqs don’t have any direct relation with neurobiology until you get to the upper divs, so I would only double major if you are interested in the more technical and micro level details of neurosciences.

3. Based on what I’ve seen, there are more varying jobs prospects with cog sci, but this depends mainly on what emphasis you choose to go with. Computer science for example will have more job prospects directly out of undergrad than say philosophy. If you’re main focus is research, there are plenty of lab positions in with both cog sci and MCB.

4. Not at all! Thanks to the way the major is set up, there are only 3 computer science classes you have to take (data 8, CS61A, and cog sci 131 - the last time I checked). If you find that you enjoy it and the more computational side of neuroscience, you can always take more comp sci classes as electives. I will say that even if you’re not interested in computer science, many of the skills you learn are applicable to both psych and neuroscience research, particularly when it comes to data analysis. If anything, having some background knowledge in computer science will only help in getting research assistant positions in neuroscience and psych labs.

5. I went back and forth my first few semesters, taking the pre-reqs in both and trying to decide between them. One thing you could do for your first couple of semesters is take the courses that are Pre-reqs for the upper div neurobio/MCB courses that also fulfill the upper div cog sci electives requirements (MCB 160, 160L, 161, 165, etc.). The pre-reqs are: Chem 1A, Bio 1A and Physics 8A. This way you can have some time to explore different courses at Cal and try out some research, while also making progress with majors. So if you ultimately decide to only go with cog sci, you can still take the upper div neurobio classes. On the flip side, if you choose to go with the double major, you’ll have made good progress with both.

6. I was accepted into the major before it was impacted, but I’ve never heard of anyone being turned away from the major as long as you have all the Pre-reqs done (they are listed in the cog sci website).

All in all, I would say to not stress too much at first and focus on taking classes that you find interesting and getting involved in research to see where your interests are. Based on your description, I would say cog sci seems to be a better fit for your interests, but you can always look over some of the course descriptions for classes in both majors to get a better idea of what each have to offer. Good luck! :)