If e-filed a federal amend and oped to electronically pay. Why are there instructions in my docs to mail a form and payment? and no address to send it to?

You are amending?  If you can pay electronically that is new.  You always had to send in a check.  But ignore the 1040V either way.  

Go by the actual 1040X.  Line 18 should be your original refund amount and line 22 should be your additional refund.  If you paid on your original return it will be on line 16.  If there is an amount owed with the amendment, it will be on line 20.

If you have a tax due, do not send the 1040V.  Just include a check with the 1040X.  Ignore the 1040V.  That is for the original return or what the original return would have been if it didn’t need correcting.  Don’t pay the amount on the 1040V.  Pay the amount on the actual 1040X.