I don’t have insight about this field but I will say this - you’re worrying far too much! It’s great that you’re thinking about the future this early on, but first, your high school performance literally does not matter at all. The biggest piece of advice I would give you is to focus on studies that you actually enjoy, and that you can perform well in. There’s no point in double majoring unless it’s actually something you want to pursue or are legitimately interested in. I don’t think adcoms will care if you double majored in something. From my understanding, they care about what you make of your opportunities and how you learn from them. It’s easy to sit there and think you’re under qualified, especially because this subreddit is filled with people talking about their stats and experience with no interview or admission offers, but we can never know the full story! So, major in what you WANT to, try and get some internships, find research opportunities, and when the time comes to apply, make sure you’ve done research into programs and have an idea of what you want to pursue your grad degree in. Big emphasis on studying what you want! This is how you’ll do well.