Its wild that THAT is where the line is wrt giving drugs to children, particularly in the context of giving kids incredibly powerful, schedule-class stimulants

Yes. One difference is that a number of legitimate studies have linked consumption of THC by those in certain developmental stages with functional deficits in later life (as with alcohol, and FES is definitely a thing). Of course, a rigourous scientific experiment would give definitive proof but would be unethical.

Are there similar studies regarding the ADHD meds?

I suspect the kind of poorly-controlled, correlative studies done for THC would also show correlation between ADHD meds in childhood and a variety of functional problems later in life. (The known comorbities of ADHD alone should account for that.)

Definitely not. Smoke is bad for the lungs.