We just took our friends from North Wales out for three days in South Wales…. they stayed at the Afan Lodge:
Day 1: Penhydd and Y Wall
Day 2: Skyline
Day 3: Whites.. (half day as driving back)
Have to say Skyline is a monster, but for me the best trail at the forests – feels very natural, and some really stonking singletrack. Just take a load of food and water 🙂
They loved the whole trip, and thinking about it – te first time I did the trails I loved them to bits.
Where are you staying? If it's at the lodge, then Brecfa is at least an hour away and the same for Cwncarn…. so two hours extra in a vehicle when you've already driven down… up to you, but for me on a first visit the Afan and Glyncorrwyg centres have enough to keep you busy for three days.