This is exactly how I studied for hard (theory-heavy) exams at the university! If this would cover >90% of what can come up on the certification exam, I would be willing to pay! Please take my money!
AWS Professional Services here -- we all study for our cert exams using the site acloud.guru. They're not always perfect, but generally pretty good and handy for spot study. May be a good choice if you want to go deeper than these flashcards. AWS also offers in-person training sessions that are quality, but I'm not sure what the status of those are given the ongoing pandemic.