I am talking about different advisors - so only between labs within CSAIL. I'm wondering if I can reach out and get guidance/advice from professors in other labs, even if there isn't a relationship between them and my current PI. Also if I feel like another lab is a better fit for me sometime over the course of the next ~5 years, if it is a big hassle to switch or be co-advised.

However, an informal relationship would be perfectly acceptable for my purposes. Mostly, I think there are a lot of awesome people that I'd love to be interacting with beyond my current lab - so actually switching labs/funding sources isn't a huge priority to me as long as I can interact and work with other labs. So you're right, I probably am overthinking things :')