HT550 route or parts of it. There’s a thread on Bearbones about the best bikepacking route, someone suggested the middle loop (the northbound and southbound routes meet at two places effectively creating three loops) from Ft Augustus up to Oykel Bridge then back down through the Fisherfield Forest, Torridon and Glen Affric. It’s around 400Km. The southern loop, new route this year, is around 250km and Alan G reckons that will be a decent one to do on its own as well.
Not much bog though there’s an interesting river crossing in the Fisherfield forest.