I do wrap earlier at comps, but for home cooking 170*-75* is what we prefer. Not so much the moisture, cause I have a good quality brisket and has had phosphates injected into it. While at comps judges don't mark down for the lack of bark and we dredge our slices for added flavor, but at home I like a nice flavored bark. The wrapping later lets the sweating process build a better bark and while it's not a proven fact, I feel that you don't lose as much flavor out of wrapping by doing it at that time.
You can tell the difference in texture of the meat by which temp you wrap at, it will be more pot roast texture if you wrap quicker...yes it may hold at little more moisture, but not a considerable amount.
Yeah, lots of fat in the point that needs rendering and phosphates tend to slow that process down or at least I feel it does.
As far as fat cap, I like it between the brisket and the fire....if you are cooking at higher temps, you may need to flip it though, especially if you run it naked all the way. When cooking on the electric I run it at 240* and on the FEC I cook at 180* for 8hrs and then run at 260*. The 180* is for timing purposes and adding more smoke to the insulated cooker.