I have taken the 350 (gare de l'est) and 351 bus (nation) numerous times to cdg and I have never had the bus driver enforce limits of any kind. Depending on when you go you may be the only person on the bus. For example, I took it one Sunday morning at 6am and it was me and one other person. It ended up being a quick trip around 45 minutes! No traffic, no people and cheap.
If you buy the tickets on board, it's 1.90e per ticket and you need 3 tickets for a total of 5.70e. If you buy the tickets in a carnet (10 tickets for 12e) the cost is reduced to 3.60e.
I think these buses are the best kept secret!