We did the Loch Affric loop in June from the Forestry car park. We did the north side first, then back along the fire road. There’s some pretty big drop offs and rock gardens on the north side, but I was able to negotiate them fairly easily on the hardtail with our 2 year old in the WeeRide. I did get stuck in a bog though up to the axles though. It’s probably doable on a gravel bike, but I’d rather have a MTB for it.
Oh, and the deer gate is locked and you have to lift the bikes over it as they won’t fit through the kissing gate. There’s various access issues with the Estate up there at the minute, which is a shame and the bridge outside the lodge is a no go for non-residents of the Estate.