Sure, it will work if you secure them well. The cage you mention looks pretty bomber, but I would bolster it with some sort of strap that surrounds both the fork leg and bag as opposed to solely trusting a cage mount. Maybe NBD, but it sucks seeing cargo falling off your fork in the BC, and there is a good bit of rough terrain on the CT (and I presume the other trails you mention).
Considering the light payload that lowers-mounted bags usually see, and their limited capacity, If I'm going where a squish fork is de rigeuer, I'd rather put that cargo almost anywhere, including on my back. The best MO is to pare down the kit to eliminate the need for the fork-mounted bags. Trails like the ones you mention are more fun with less gear and the most nimble setup.
FWIW... Mainly, just go ride and don't bail.