I was at both a couple of weeks ago. Cwmcarn is fine, usual brake bumps on the decents at heavy braking points. Afan is running nicely too, did both The Wall and Whytes. Wall was great fun on the HT as was Cwmcarn – was catching up most of the riders on full bouncers.
Whytes is a different story – I struggled on the climb, with the HT getting knocked all over the place. Coming down was fairly eye rattling too. Would definitely have preferred a full sus on that. Most of the last couple of kilometers were picking lines through a very rocky decent, where a full sus would have floated over most of it.
In short, all do’able on the HT, but I’d probably take a full sus for comfort.