"Be it" means "whether it is" or "whether it be"
We use it to describe something you will do for sure but how, when and where may not be certain. Your example sentence is a perfect example of how to use it. Here is another similar use: "I will watch that movie, be it this week, next week or the week after" so you know you'll watch it but you're not sure when.
I would say it's formal, yes, though not strictly speaking.
Hope this helps but please let me know if you have any questions.