When a person diagnosed with Adult ADHD takes medication for it...?

do they just appear normal? Like does it stop the fidgeting and hyperactivity completely? strike up the concentration and lower the distraction down to "normal" level? Stop speaking too much and stop being so random? Not appear to have any ADHD symptoms whatsoever?

It helps a lot with those things, it also helps them sleep better. Most adults and children with ADHD have problems with insomnia, the body is tired but the mind won't quit. Some use Melatonin, an over the counter product to help the body produce more melatonin and sleep better.
Taking the proper ADHD medicine will help with the fidgeting and the distraction, will help the person calm down and be able to focus properly. As your body adjusts to the medicine you may appear quiet and very calm at first, then your body will adjust and you will be normal with the benefit of being able to hold your attention on a task for say work and complete it.

i know of a guy in his early/mid twenties that takes medication for adult adhd and he doesn't fidget. he's not overly hyperactive, but he does still have slightly more energy than the average adult. but it doesn't come off as someone who is displaying adhd symptoms....it just appears that he's very active. he is able to concentrate pretty well. the only downside is that it makes him have zero appetite. almost to the point that if someone doesn't remind him to eat, he won't realize that he's hungry or that he hasn't eaten anything that day.

adhd meds help you concentrate more.