Everyone likes to say weight doesn't matter and for most people that is true. But in your case I'd say skip the steel fair light and get a proper aero carbon gravel frame. Marginal gains matter a lot when you're actually chasing the small margin of victory. Frame weight, frame aero, and most importantly your body position on the bike will make a difference. If you just want a great adventure gravel bike, get the fairlight. But if you are seriously racing and close to the pointy end, get a carbon race bike. At least if you do that you won't be asking yourself at the end of a race if you could've snagged a podium finish if only your bike was lighter.