I’ve ridden it with a group as a one day ride (the 200km Aviemore-Tomintoul-Braemar-Blair Atholl-Gaick-Aviemore route). Skipped the last few miles of singletrack from Feshiebridge to Aviemore and took the road because we were running a bit short of time.
Compared to the WHW the Cairngorm loop is all rideable (nothing like the long Loch Lomond hike-a-bike or stile and fence hopping on the southern portion of the WHW). It is mostly landrover track, with some singletrack at the head of Glen Tilt and in the forest south and east of Aviemore. The route generally follows the glens around the mountains, so there is relatively little climbing (some long drags between Tomintoul and Braemar). No major river crossing problems, unless the weather is exceptional.
The Cairngorm Loop will be much quieter than the WHW (apart from Tomintoul, Linn of Dee and Blair Atholl, I don’t think we say anyone else all day) so no problems with walkers on the path. I would say it is generally a bit more remote than the WHW, with more places where you will have a long walk out to a road if you run into problems.
It’s a big day out in the hills and forms a very satisfying natural loop, so I don’t think you’ll regret giving it a go.