I have a Brain Bag and a Camera I/O and an old Horizontal Brain Cell - size 3S (about the same size as a Camera I/O). The CI/O and "fake" C I/O (3S Hor. BC) all fit in fine into the Brain Bag.
Also, as each BB compartment is about 4" deep, it confirms that each compartment will fit a C I/O which is 3.75" deep.
Given the above, I would say that 2 Camera I/O are fine.
As for the Snake Charmer, I do not have one but have similar cable pouches. I would put it on top of the Camera I/O and not fill it up too much or it will be a tight squeeze. If trying to fit it into the side or top pockets, you would need to squish the Snake Charmer probably and not have it too full.
IMHO, you could fit a Vertical Freudian Slip - but you would not be able to fit much in it (maybe a folder with a few papers).
Hope this helps