I've made them different ways. Boiled first or not. Cubed, sliced or shredded. Crispy or not. Mostly what I do now is just cube a russet, dice a poblano and half an onion, slice a couple garlic cloves and toss it all in stainless pan on medium high with about three tablespoons olive oil and salt.
I don't get crispy potatoes without cooking the taters separately from the onions and peppers and that's just more trouble than I usually want to go to. Same with boiling the potatoes first.
My mandolin is a seldom used Zyliss with V-shaped blades similar to the one on the left in the video which she doesn't demonstrate. To see my favorite mandolins, search YouTube for Rhonda Vincent or Ricky Skaggs.
Old bachelor cook