I used to live in Forge BITD. Whilst much of what Kramer says is correct my recollections of Hengwm, between Bugeilyn and the Afon Maesnant/ Afon Hengwn confluence is huge hike a bike territory. Your socks may well get more that wet. The Afon Hengwm ford can be dangerous in heavy rain but there is a good bridge 200 m upstream.
I would not consider taking the bw running over the southwest flank of Carn Hyddgen via Banc Lleustnewydd, I’m not sure that it even exists except in some parish councillor’s imagination back in the 1950’s when the RoW were drawn up. Be very wary indeed. Google Earth seems to confirm this.
Likewise, Drosgol can be circumnavigated (on paper) but it really is ankle twisting hike a bike territory once again, albeit slightly (ha!) drier than Hengwm.
I love the place.