So relaxed (or very activated)? Generally what people think of when they say "like they're on drugs" are just normal states that they disapprove of because it suits the narrative. In this case, the narrative is "screen time is bad". That means it is suitable to condemn it by making a parallel with something destructive, to make it feel like it has some association (which it neither physically nor mentally has been proven to have).
We have some casual acquaintance we visited two or three times. Their then-4yo was constantly on an iPad on YouTube Kids, switching videos every 20 seconds. Just watching him was infuriating. You had rather innocent or mundane videos of e.g. model trains driving around, but before you could start to pay attention to any details or any kind of narrative, he'd switch to a video of kids in a swimming pool full of orbeez, then something Sesame-street-like. And they just let him keep doing that since he'd throw a tantrum if they take away the iPad. They have to let him watch that stuff at the table, otherwise he wouldn't eat. Fast forward to last year, he got into elementary school and was absolutely unable to pay attention to anything. Teachers made him see doctors, he's on medication now, but that was half a year ago so no idea how things are going today.
Now I'm sure someone will pull the "are we sure we got cause and effect right here?" card, but even if that kid had some kind of predisposition, nobody can tell me that just putting up with the kid's tantrums when he was still four (or whatever age he started at, this was just when I first saw this) and taking away the iPad, going outside more would not have significantly improved the outcome here.
Wether enough scientific fact has been gathered to understand the inner workings and circumstances are irrevelant, the cognitive weight of TV exist as a matter of fact.
Now there are of course difference between TV and monitor and screen time. What causes the problems are TV like stuff - passive, movie-ish information. Drawing lines in paint or typing buttons to see them appear on notepad is definetly another thing - the information flow and actions there are controlled by the kid and there is another huge difference if the parent is there explaining. Not the monitor itself is the problem, but the absolutely overwhelming quantities of raw information which designed specifically to catch and hold an adults attention. Kids simply have no means to absorb or escape it.
On my experience kids over 4-6 years starts to absorb some of the information and kids over 8 can sit through a disney movie with sufferable consequences.
She describes everything, she learns stuff, and even tell me about the game afterwards by herself (she is 3). The major problem is that she does not realize when she is bored or tired. To be fair, that's a problem with many activities, but boredom with toys is way more evident (she would just step away), while with videogames she would just get incredibly demanding (I can't do this, I can't do that, this is scary, changes level, even though it's stuff she has already done). She also chooses and replays the same levels to discover more (and she does!)
If the kid reads/solves and then behaves normally, then it is different.
I have observed, as many other parents have as well, that if the kids spend too much time in front of the screen (> 20 minutes, give or take), they become resistant, moodier, and worse behaved. This is not true if we're playing a board game or having reading time. So, I think a bit of moderation is important.
Incidentally, since having kids, I've also noticed that I am short-tempered if I spend too much time in front of the screen, a good reminder to take a walk a few times during the day.
2.) What you said is purely ridiculous. The "tamptrums should never happen" is wishful thinking. It is a goal to produce adult that don't throws tamptrums.
3.) Kids behavior is in fact heavily dependent on environment. Half of classroom management and child raising is literally all about that.
4.) Even many adults rage when gaming and after. Evan adults are irritable and annoyed after gaming.
This is not true and is extremely unrealistic thinking.
Also: some traits of your children's personality form very young, regardless of your style of parenting. Your influence is strong of course, but some things are just due to the way your kid is wired. You can set an example, and be firm about bad behavior, but some shit is going to happen anyway, tantrums included, depending on the personality of your children.
And to hell who said you get used to the smell. Second kid and I still breathe with my mouth during the diaper change.