Assuming your valve clearances are in spec, I would degree in the cams per the instructions that came from webcams. I want to say my cams Idle'd surprisingly like stock once I got my clearances right. I can't recall my motor pulled 20 in/hg's, or if it was more like 18 in/hg at idle.
I left the cams zero'd out since I did not have adjustable cam gears. I knew it wasn't ideal, but I really just didn't want the layer of complexity.
As I recall, I didn't need to add much (if any) fuel at cruising. The AFR's went a little leaner, but there was no mifire so I left the part-throttle map alone. As far as the WOT, it will be completely different since your torque curve will change dramatically due to the cams. I started with a brand new fuel map in boost, made sure everything was level and smooth, and added about 5% more fuel on top of what was already there. It wasn't very difficult to get the AFR's dialed in from that point.
The thinner HG should not affect your AFR's, but your cams definitely will.