Yes, there are different ferrules for different cable housings, but brake housings are all 5mm OD these days so doesn't matter one bit.

What matters is that newer Campag Ergo and aero brake levers require a 6mm OD ferrule, whereas Shimano aero and STI levers should never have a ferrule on the end of the brake housing, since the lever body is sized for the 5mm OD housing. I often have to extract ferrules from Shimano levers that were mistakenly fitted and prevent new housing from seating in the lever.

For shift housings, brand matters and Campag housings have used an odd 4.5mm housing that requires their own ferrules. The ferrule OD is the same for all shift housings tho, so a Campag or Shimano housing can be substituted if the corresponding ferrules are used, as per zukanh1.

Yes, 2m of housing will be more than enough for f&r brakes.