I did something similar a few years back and let me tell you, no regrets. No lingering worries that maybe this is the time that one wanker will decide to out me because who the fuck knows why. My new namespace name has a pretty decent rep now and I have zero regrets about leaving the old one behind.
Yuletide is, if anything, the best exchange to reinvent yourself in. Some people may wonder if you're a sock, but nobody's going to hold it against you. (If you're very worried about people thinking you're a sock, you can create a Discord account, DW, whatever and drop that you're coming back to fandom after a while away, but honestly, I don't think it's worth the effort.) And once you're through Yuletide, you'll be an established account.
Re: Is an AO3 account not enough?
Yuletide is, if anything, the best exchange to reinvent yourself in. Some people may wonder if you're a sock, but nobody's going to hold it against you. (If you're very worried about people thinking you're a sock, you can create a Discord account, DW, whatever and drop that you're coming back to fandom after a while away, but honestly, I don't think it's worth the effort.) And once you're through Yuletide, you'll be an established account.