Hi. I am much older than you. I've dealt with my naturally curly hair for decades longer than you have, and this is what I would suggest. If you would like your curls looser, try a curling iron when your hair is dry. Taylor Swift does this to tame her waves. If you are opposed to heat try using a deffuser on low to soften the tightness of your curl.
I have a good friend who did a BKT. She had straight hair naturally, but it was getting frizzy and wavy with age. Wow did it work well for her. Stick straight hair with bangs that she just washes and wears. It always looks great. Just the hair us curly girls want, but don't have.
Since you are so curly, I think I would avoid this. The grow out will be a mess, and it's a lot of money to maintain the look.
Try a straightening product. This really does relax the curl. I use John frieda Straight fixation. Let us know what you decide! You have a lifetime ahead of you to master your curls. Hopefully you can do that now!