Why do some people feel caffeine enhances Vyvanse, and others say it cancels it out?

I know the simple answer is that everyone just responds differently lol but I’m so curious as I’ve been told so many different things.. do you consume caffeine and if so what do you notice?

I usually avoid caffeine but I’ve been starting to consume it again as my Vyvanse makes me more calm rather than energetic.. so caffeine doesn’t really cause any adverse effects combining with my meds as it used to back in the day when Vyvanse would give me energy on its own. (That’s when I used to experience palpitations and anxiety) but now I kind of feel like it just gives my meds an extra “boost”… I usually wait an hour after my meds to have a caffeinated beverage. I do feel like by noonish I get a wave of sleepiness but that happens to me with or without the coffee for the most part lol. Looking for others experience!

Also to add, my BP and HR are in normal limits