Good morning, and welcome, krh.
I am no expert on what you are asking, but hang on.
As people wake and log on, I'm sure you'll get plenty of feedback.
As far as fries go though, it's my understanding, from watching food shows, they dip potatoes in very high heat fryer to "seal" the potato, raise it out, then dip it again to "cook" the inside. This keeps them "healthy" because the oil isn't absorbed into the potato.
Another tip is, they don't put so many in at a time, so
as to NOT lower the temp of the oil too much.
I make sweet potato fries on the stove, in cast iron skillet, with about an inch of peanut oil, on as high a heat as my electric stove gets, and make sure the outside of the potato is DRY before putting in oil, so they don't splatter. I do batches, and then remove them to cookie sheet, to a warm oven, til all are done, kosher salting as they come out.
Good luck with your quest.