Sissy is 6 and 1/2 months old and she has just graduated from being a "walking pooper" as you put it
She also went through a phase where if she had any choice, she would piddle on anything that felt like a pad, carpet, blanket, scatter rugs. I picked it all up, woke her from her crate, placed her inside her playpen where I kept the "main pee pee pad" then when she went, would clap and play with both of them. One mistake I made was moving the pads (I keep one in the family room, they like this one best-it is hidden for their privacy (they both stop going if I stop and watch them

, then the one in the living room area where the playpen "used to be" I moved that one, thinking to eliminate it, she went on the floor where it was
You are right, can't scold them if they start on the pad, Chloe was about 8 months when she got it right, Sissy is grabbing it at 6 months. The biggest mistake besides moving those pads, is giving them freedom to roam all around when your eyes can't be on them, that's when they pee pee without warning I have found. So 2nd time around, I did the playpen thing. To protect the carpets from "walking poopers" I got a matress protector from ears, the flat ones-not with fitted corners, I use it upside down UNDER the wee wee pads, then If you get a walking poo, it still is not on the carpet. By the way, I have to put down 2 wee wee pads, one right next to the other. My girls do not like to share the pad

, yet they share food, treats, bones, toys and ME
P.S.AND BEDS!!
P.S.S. and to answer your first question, I think each doggie is different, just like human kids. My Chloe would not poo outside, she would cry to come back in to use her pad... Sissy on the other hand does go outside if that is where we happen to be. Both pee in or out. I wouldn't leave them outside alone for anything tho, you are taking a chance there I would think, hawk, squirrels, skunks, owls, humans, humans, & humans!!