I would use a pseud if you want them sort-of-but-not-quite associated with your username under AO3. When you post works on AO3 under pseuds, they will show up as: "pseud (magistrate)." So the works will be recognizable as yours, but readers will know you've separated the fic off for some reason.

(Here is an example of someone I follow who uses pseuds, if you wanna browse to see how it shows up.)

Otherwise, my general method is to post them quietly under lock on a private journal, but you seem to be a tad more confident in your own writing. ^^