Hi! As I was reading your post, I realized how similar we are- I started learning QWERTY in 4th grade, and I play the piano, as well. I'm just a little behind you in age- I'm still in middle school (unfortunately).
To start off, I would recommend reading the "can't pass the 75 wpm limit" forum on KeyHero. It has some pretty helpful tips that can be very useful to read into. However, I also have a few tips that I would recommend to you that I've learned myself. So here goes:
1. Keep practicing. One of the reasons that I can type 130 WPM and haven't been practicing typing for a long time at all is because I used to slave away at the computer, constantly typing. In all honesty, this definitely wasn't very healthy for me, but whatever- it's a totally legible tip to learn typing. Through experience, however, I have discovered that you shouldn't type all at once- TAKE BREAKS. Breaks will help your mind to process the memorization of the keys, and will seriously help you along in gaining a higher WPM.
2. Type in blocks. A tip I've found to be very helpful is to first focus on getting accuracy, take a break from typing for a couple of days, to then type as fast as you possibly can. Keep repeating this cycle, and I promise that you'll get some great results. Something I also like to do is to log off my account, so that when I focus on accuracy and my WPM isn't as fast as it normally would be, it won't factor into my overall WPM growth chart.
3. I'm guessing that you've already memorized your keyboard, since you can type at 80-100 WPM- but if there's some words you find yourself lacking in speed on, make sure you practice prompts that aren't entirely words. A major problem I've seen typists have is that they memorize words, and not characters. Make sure you don't run into that problem.
4. Compete! The only reason I'm fast at typing today is because I used to be ridiculously competitive in fourth grade. And I'm glad that I was- competing on sites such as TypeRacer allows you to focus completely on typing the best that you can, and really puts pressure on you to type better. This method causes you to increase in speed by a LOT. I recommend it!

I might've written a lot in this forum post, but all of these tips have helped me to reach the speed that I can type today- 130 WPM in 2 years. I'm pretty proud of it. And, especially because our situations are so similar, I'm positive that at least one of these tips will work out for you! Good luck on your typing journey.
I feel like I just wrote so much, I should sign it, so here goes.
Sincerely, -boi

Sorry this is a late reply, but thank you very much for your very helpful tips. I will keep all these in mind for my future typing adventures. I have been starting to play NitroType with friends and with randoms to try and give me a motivation to try and win the race. And I find it very cool that we have such a similar situation and am grateful that we are since you can give me such great advice! Good luck on your future typing adventures as well and hope you keep on improving too!

Hey, I myself feel like i've hit a plateau of 80-85 WPM and can't seem to cross this no matter what. I initially thought of changing my keyboard type to something like the dvorak but now ill try the compete thing you suggest.
Your 3rd point it easy to understand but difficult to change. I would rather suggest that one remember more words by heart rather than take the long route to do characters.

Thanks
*In Krato's voice* boi

Again, the forum called "can't pass the 75 WPM limit" is a pretty dang good forum! Especially if you're hitting the 80-85 WPM area and can't seem to get around it. It'll definitely be pretty helpful.
As for the 3rd point I made about memorizing the keyboard- I guess that either side can be right, but if there's any names or words that pop up randomly, and you must type them, a lot of times typists will have a hard time doing so, which is why it is so important to memorize the keyboard. That's just my opinion, though! Most people don't have to type a lot of words like that, but it can be pretty helpful to memorize. When you've fully memorized all the characters, though, you might want to start memorizing words.
Also- good reference. "come here, boi"

Number one thing to do is to practice every single day. This helped me get to the fast typing speed that i am today, which is 123 wpm the last time that i checked.

I have been playing piano too, and yes this helps as i can maintain good typing speeds for long typing sessions. However, i do not have the greatest rhythm when playing piano.

Yes, focus on accuracy and not speed. This will help you to type better at lower speeds, so that way you can achieve a higher speed.

Cherry MX Brown is best for you if you want to upgrade.

Thanks for the great advice!