Yes, beardies are wonderful eaters. Nothing like these picky ball pythons.
The more adults you purchase the more quickly the colony will get going. If you've got some time on your hands, you'll be fine starting out with only a few adults plus a ton of mixed. I don't remember exactly, but I think I got the 120 mixed originally, and there turned out to be many more older roaches than younger ones... I think I had at least 3 big adult pairs instead of one.The roach diet and water crystals are really handy and easy and probably some of the better gutloads out there, but fruits work just fine. Don't give them a water dish; they will drown! Water in fruit plus occasional misting is usually good enough, but if you want to, providing a wet paper towel is also good.