I did a similar loop around Issyk-Kul last year and it was unforgettable. Just a heads-up on the driving culture: local traffic police (now called the Patrol Police) are quite active on the main highways, so strictly follow the speed limits, especially when passing through villages. Also, outside of Bishkek and the major towns around the lake, gas stations can be few and far between, and high-octane fuel isn't always guaranteed. Download offline maps like Maps.me or 2GIS before you head out into the mountains because cellular coverage drops completely once you enter the canyons.