Generally the drive up is pretty good in good weather. Looking over the side of some of the roads isn't a little hairy, especially Montsegur and Queribus. If you're worried about the drive, approach Montsegur from the Montferrand side and Queribus/Peyrepeteuse from the Bugarach side. For the walk, from hardest to easiest, to the entrance gate. Montsegur: 45 minute walk from car park, very steep at times, off season can be foggy/snowy. Shops and cafe in Montsegur village below. Queribus: 20 minutes from TOP car park (take the road till you can't go any further), moderate slope, steep inside the castle, it's exposed so difficult when wet or windy. Shop at bottom. Puilarens: 10-15 mins from car park, steep but cool, sheltered climb. Shop at bottom. Generally not very busy. Peyrepeteuse: 10-15 mins rolling up and down walk through woods and round a ridge to first entrance. Can be difficult when wet but not too hard otherwise. Walk up to second castle inside the first is pretty steep and slippery when wet. Lower parts pretty sheltered. All have their own character, but I'd recommend Peyrepeteuse as a good one to try first as it is architecturally the most interesting.