As someone who actually has an academic background in such subjects, ADHD medications like methylphenidate, lisdexamfetamine and adderall operate on fine tuned clinical doses, clinical doses do not trigger those little spiny D1 neurons in a certain part of the brain that you'd see in recreational doses, nor are they sufficiently large enough to cause a "high" or euphoria. They essentially just restore certain levels of neurotransmitters / activity / expression often deficient in ADHD patients to normal or optimal levels, and as a result, you also tend to see positive changes in the associated brain regions as their function conversely returns to normal or close to normal.

ADHD stimulants for the vast majority of ADHD folks are life changing, because it allows them to go from struggling to function and the smallest of normal tasks feeling like a monumental task... to normal. The most ironic part is that individuals with ADHD who follow a prescription of stimulants have reduced rates of substance abuse.

In the world of pharmaceuticals you have "dose–response relationship" or dose dependent effects, this means drugs don't work linearly in the sense of X drug always has X altering properties, but X altering properties increase with dosage, it means X drugs often has different X altering properties at different dosages.

The misinformation around ADHD stimulants has been I think some of the most poorly handled medical topics in recent history, between people thinking it's highly addictive / damaging because of it's molecular make up, to the amount of people trying to rort the medical system for cheap stimulants, to psychiatrists and GP's with archaic ideas that it can't be diagnosed in adulthood, it's a mess.