First: there are no rules. You have to determine what you want it to look like.
Here is “Cory’s question about heels-elevated squatting” that was referenced in the video. [link]
Sometimes a wider stance will allow someone to keep their heels down. But it does affect their guts and how they manage their center of gravity.
You might try starting people in a seated position and instruct them to stand up. They will tend to find the stance that allows for the most motion. If you deem it safe, you can keep it. “Potty squatting.”
They need to learn how to manage their center of gravity. They need to learn how to access their mobility. Sometimes you just need to shut up.
I don’t have a set way to choose a squat or deadlift stance. I just decide what I want to get out of this squat or deadlift, and then find a stance that will allow for that.
I would hope that the long-term goal is to be able to squat in several different ways instead of one “perfect” way. A front squat is different than a back squat. They require movement variability. This is generally healthier, though may not lead to maximum performance in a given context.