My question for you
1. How do an international candidate get enrolled in these programs?
I would imagine the same way as domestic applicants, you would just have to sort out travel and/or moving to accommodate this.
2. What additional exams might be required for these degrees?
Depends on the program but whatever independent tests required for each degree i.
e GMAT, LSAT, MCAT, etc
3. Value a joint degree brings over a traditional M.B.A
This will depend on your career goals, so this is the self-reflection portion of deciding to go to grad school. There should be some rationale for why you are pursuing a grad degree that only you would know
4. How to Juggle these two degrees (Or how to do well in both of them).
Many programs you focus on one year of each program at a time so it is easier to focus but again this is a program by program situation