The P-09 seems to have exceptional mechanical accuracy from what I've read. Out of the box the omega trigger on the P-09 is probably better, but the SP-01 trigger might have more potential for improvement with cz custom or cgw parts.
"The new factory barrels need to be fit at the breech face, but a used 9 barrel will drop right in a 40 slide."
Why will a used 9 mm barrel drop right in to a .40 slide, but a new barrel would need to be fit?
An accu shadow has no pin because it would interfere with the threads. And the screwed in bushing prevents the front sight from moving. A regular shadow has the normal bushing, and the front sight pin holds the front sight and bushing in place
Yes they are crazy tight. I tapped them partially on and off a few times because I was also afraid they would get stuck on and be too difficult to remove. Some lube might help.
The factory front sight is 7.5 mm (as cz measures it). I would shoot it with your load first and see where the bullets impact before ordering a FO. A 1 mm difference in front sight height will make about a 2 inch difference at 10 yards.