Yes we do have multi wire branch circuits as you describe but if I was doing it I would not use a 2 pole breaker since the cost is more than double a 1 pole. For GFCI we generally install a GFCI outlet at the first outlet and seldom use a breaker. IE normal 1 pole breaker and GFCI outlet at the first required location. No common trip is required for a 3 wire circuit unless the devices are on the same mounting strap like as for split receptacles. It is possible to run 2 circuits from 2 X 1 pole CB on different buss with 1 neutral and a GFCI outlet at the first receptacle in each branch. Obviously the neutrals cannot share beyond this point or the service guy will slap someone on the back of the head ;-)
An AFCI circuit requires breaker protection as the entire branch must be AFCI protected. The only outlets required to be AFCI protected are the bedroom Plugs only. No smoke alarms may be on the circuit and lighting may be on the circuit. The cost of an AFCI 1 pole breaker was around CDN $70.00 and 2 pole around $250.00 even for a long home run it is still much cheaper to run 2 circuits.
