Hi! I'm also gonna share my story, if you don't mind-
When I was 12, I joined a really toxic online forum. I didn't become outright bigoted, but i did say some really terrible shit in the effort to become "cool" and the thought that hey maybe being offensive is actually really funny (it's not). At the time, I thought what I was saying had no weight to it because... "well, it's online and I wasn't trying to be racist/homophobic/offensive!" I left said online forum at 14 after someone rightfully called me out for being a complete asshole, and I had an epiphany that the place sucked and I was just not being my best self there.
This was almost two years ago. I'm 16 now, and sometimes I think just like you, I'm also be worried about someone digging something up and trying to cancel me, even though the forum flushes out its posts all the time.
I think my advice is kinda the same as everyone else's, take down what you can and start over. I've kind of learned not to stress AS MUCH because even if someone finds out, and I give out whatever message I have to, people hopefully will see I no longer act like the way I did and that I've deemed those things offensive now, and that there are always people not willing to see someone's changed. It's happened over and over again with other people who twitter dragged up their years old problematic tweets for, people either sympathize and are willing to move on, and others not so much. I think as long as you aren't like, Shane Dawson or anything, you're good.
tl;dr as long as you've recognized you've changed, and that your behavior reflects this, then most will see that anyway. Just start over