But adderall and vyvanse aren’t the same drug at all. You cannot directly compare dosages. 50mg of vyvanse is roughly equivalent to 20mg of adderall. As a prodrug, Vyvanse must be processed by the liver for it to function.

Indeed. That's why I'm underscoring that my Vyvanse dosage is only midly higher (5mg) than my Adderall dose was a few years ago.