As a parent, who is completely conscious of everything going on around social media and technology, you will absolutely need to step in

Oh absolutely. My point is that supervision should be as low-touch as possible. Let kids screw up when the stakes are low so they don't screw up later when the stakes are higher.

As a kid, I got into things I shouldn't have online, mostly because we only had dialup so I would wait until everyone was in bed to use the computer so I didn't disrupt phone calls coming in. I ended up getting caught, had a productive talk, and learned what to avoid. That was really effective for me, and the lack of firm guardrails got me interested in learning to computers worked, so I taught myself basic webdev as a teen, which launched me into a software dev role.

If we had strict rules preventing computer use, yes, I probably wouldn't have gotten into things I shouldn't, but I also wouldn't have had the freedom to teach myself software dev and probably wouldn't have gotten interested in it.

you WILL have to be the parent who sets boundaries on the stimuli their brain craves but has a negative impact on their overall health

Oh, and I certainly do, but I use a carrot and stick approach rather than a "guardrails" approach. I tell them what the rules are, but put nothing in place to prevent them from breaking the rules, and when they do (and they will), I'll completely remove access for a time after a discussion about why the rules exist. For example:

• video games - we have a system where the kids "earn" playtime (we do it by reading books), and if they go beyond their allotted playtime (we have a max of 2hrs/day), they completely lose the privilege (I take the console away)
• bedtime - we got them watches w/ games on them and told them they couldn't use them at night; we caught them using them at night, but let them continue and when they were late getting up, we pointed at the watch as the issue and took it away for a while; now they don't stay up nearly as late w/ their watches
• coming home on time - kid wanted to go to the park alone, so we told them when to be back; they came back late, so I took away their bicycle (that's how they got there) for a while saying I don't trust them to come back on time; now they come back on time, and they can ride their bicycle pretty much wherever they want (we have boundaries)

That's how I was raised, and I found it incredibly effective. I almost never had things taken away as well, because once they showed they were willing to, I tended to listen and follow the rules.

You don’t instill healthy eating into a child by giving them unlimited money and telling them to make their own decisions.

Sure, but you also don't instill healthy eating habits by not letting them make poor choices either. Let kids fail and fail hard (i.e. don't catch them), but be there to help them back up.

For example, let them eat as much Halloween candy as they want for one day, and then when they inevitably get a stomach ache, they'll learn why moderation is important. Likewise with money, if they waste it all on something stupid and don't have enough for what they really want, they'll learn the value of delayed gratification.

The more natural and immediate the consequence, the more effective it is at teaching them self-discipline.

Obviously, protect them from the worst harms (e.g. we don't let our kids play w/ knives or fire), but let them try and fail while the stakes are low.