A W4P is to tell the pension or plan how much withholding to take out. You don't need that unless you want more or less taxes taken out of the withdrawal or pension in the future. Yes you need to fill in box 16 if you have any state tax withholding in box 14. It won't affect your federal or state return.
If you have state withholding in box 14 then enter the same amount as in box 2a. If box 2a is blank use the amount from box 1.
