OP: It can be confusing because companies don't always group skis in the same way, and I'm not an Atomic guy anyway. Agree with Tog you should ask whether they are FIS compliant juniors or rec racing. I'd guess the 176 might be, not sure about the 174. Companies keep changing the lengths one year to the next even when they don't need to.
FWIW, "junior" has a couple of meanings. If you're looking at a mid-170's race ski that says "FIS" on it somewhere, it's not a junior ski in the sense that tweener racers use it, it's a USSA and FIS sanctioned racing ski for 14-16 year olds who are better than most of us on Epic, just lighter. These skis typically have sidecuts in the mid teens through low 20's, depending on length, and somewhat softer plates than a true adult FIS ski. They never, as far as I know, are shorter than 170 cm, companies stop these at 175 or so because your next step should be adult FIS models. These, basically, are the ski you should be looking at given your mission.
True WC GS FIS skis for adults have radii that begin at 30 m and 182 or so for women. Too much for your mission and course.
Companies then make rec racers for club and league and some Masters racers. These tend to begin in the 170's and go up to say 185. They will not say "FIS" on them, but typically do say "WC GS." The radii will be in the teens to very low 20's. These are also OK for you, but you may want them a bit longer, say 180-185.
OTOH, if the ski is in the 160's or sometimes up to 170, and doesn't say "FIS" on the topsheet, it'll be an actual junior race ski designed to be bent by kids in the 12-14 year old range, softer plate, much too flexy for you. Again, not a starter. But these junior race skis will have radii in the "cheater" range at their longer lengths, say 165 or 169. Yet they're not "cheaters," which are adult skis with hybrid SL/GS characteristics, typically a bit more on the GS side, and too stiff for a tweener to bend.
A "cheater" might also work for you, but it'll tend to have a recreational flex pattern even if it's stiff (see below). This is OK for Cross models, but in a course with gates, may not work well.
The flex pattern of racing skis are quite different from recreational skis; they're not just stiffer longer/shorter versions of a carver. Race skis tend to be particularly stiff in the tips and tail, but relatively less stiff in the middle. The opposite of a rec ski. So this is one reason why race skis can be odd at best just cruising on a groomer, and a serious handful in bumps. Conversely, this is why even a stiff rec ski will not be as capable in a course. Too quick and unstable at the tip and tail when you hit ruts or rubble, a beat too slow to flex in the belly of the turn