I can't recommend the route from Meikle Bin to Tomtain.
The ground becomes extremely boggy (step on the wrong spot, and you'll sink halfway to your knee, type of bog. Which I did.) from the tree line of the south face of Meikle Bin, followed by a short steep hike to Black Hill. From here the walker's path isn't well defined and its flanked by steep swathes of moss which grab at your pedals. We did this route using E-bikes, and we were glad to have the ability to use half-pedal strokes to boost our way through the parts where we unable to do a full rotation.
Other parts of the route are repaced with tall banks of reeds which again is boggy underfoot. However, not as severe as before but you still wouldn't like to put a foot down.
After finally reaching Tomtain, the views are just as spectacular. From here, the path leading to Carron Valley is well defined, for 100 yards or so...but then disappears. I had to rely upon my Garmin to keep me on course. The only option available is to push through the remains of felled trees to the fire road.
If I was to do this route again, I would descend the east face of Meikle Bin and follow the forest road to Carron Valley.