I’ve done part of it when I cycled from Nairn to Pitlochry, I’ve also ridden a few other sections from Culloden, Moy, Tomatin, Carrbridge etc. There are a few wee hills – such as the one between Daviot and Moy, and after Tomatin. Depending on the time of year, there’s a likelihood of a headwind – avoid the Lands End to John O’ Groats record breaking season…
I rode it on a fixed wheel, which wasn’t ideal on the narrow ‘off-road’ sections, but it wasn’t too bad. I was able to make up time on the road, and just trundled along on the paths over Drumochter. On that occasion I cycled the back lanes through Cawdor, Grantown, Coylumbridge etc, and picked up the path at Ralia. It was 100 miles to Pitlochry. At the time I was used to riding audaxes, so was fine with that distance. However, it might be more enjoyable to split Inverness-Perth into two or more days, and have a few café breaks etc.