The Micro has all the micronutrients and all the calcium. It also has all the nitrogen when using the Bloom with it. The Grow also has a little nitrogen in it, so you get a bit more nitrogen in the veg phase. You wouldn't use all 3 together. You would use Grow + Micro in veg and Bloom plus Micro in flowering.
And about the Lucas formula. That's just one guy's personal preference. If you want to copy that guy instead of following the actual directions, that's your call. I follow the directions on my nutes, personally, or usually use a little less than specified because it's medium in pots instead of recirculating so it gets stronger as water is absorbed. I figure GH probably knows a little more about how to use their nutes than some guy. I just use the FloraNova one part though. Messy but works well and less bottles around.