Won't it be player specific depending on how strong/weak their grip is?
Kinda like how some players bow their wrist quite a bit at the top of the backswing and others are flat or even slightly cupped. I believe those are byproducts of their grip, or at least they have a grip that works with their desired wrist positioning.
It's somewhat difficult to say without seeing a swing of yours, but good chances are there are probably bigger things that need improvement in your (and just about every other amateur player) swing rather than the exact positioning of your lead wrist at impact.
My question is does the back of the left wrist need to point at the target at impact or can it be facing the right of the target. I have found that I have to strengthen my grip to hit it straightish. For the life of me I can't supinate my left forearm enough to have it point at the target at impact. Is this a match up thing with my body anatomy?