I’ve just done the Tour of the Cairngorms, not to be confused with the Cairngorms Loop ITT but the route is on the Cairngorms Loop Website. It’s 122 miles long but I did an extra 10 with a diversion off route to get dinner and some nav errors. Took 2.5 days at touring pace nearly all off road. More than doable on a gravel bike with 3 bits of Hike-a-bike but they weren’t arduous. It was actually easier than i thought and a great route for a first multi day trip. Also being a loop the logistics were easy. The start Blair Atholl has both a train station and a free car park that’s safe to leave a car in for a couple of nights. It’s an awesome route with really wild isolated sections, amazing views and a great way to see the Cairngorms. Highly recommended
by No_Summer_1838