A couple of notes:
* Starbucks does not have the highest caffeine amount of major coffee chains (see https://www.timeout.com/uk/news/revealed-the-coffee-chains-with-the-most-and-least-caffeine-in-their-cups-020123 and https://www.buzzfeednews.com/article/leticiamiranda/who-is-the-king-of-caffeine)
* Light roasts may or may not have more caffeine - https://www.kickinghorsecoffee.com/caffeine-myths-dark-vs-light
* Crema isn't a layer of fat but a layer of carbon dioxide bubbles, kinda like when you pour a can of soda over ice - https://www.nicolebattefeld.com/post/what-is-crema-and-why-is-it-important