So I am a huge league fan. I also like D&D. So content from league that can be used in D&D is amazing to me. I personally want to make a path of the depths barbarian for an upcoming campaign I will be in. While yes I can just make it myself and use it for myself, it would be a lot faster and more simple for me to just follow someone else who has made everything already. Im pretty new to D&D Beyond's formatting, so someone else can probably make the content better than I can. Will we be able to publish content that "Is too similar to" the league bilgewater content? Or because it was savable before August 10th, it will forever be similar content.

In general the rule is: If you didn't originally make it - you can't publish it. So the answer is almost certainly a very resounding no.

Published?  No.

Do people have private archived copies of it they can share with other players in private campaigns?  Potentially.  Such people are not allowed to advertise that they have archived copies of the Bilgewater subclasses they can easily proliferate via content sharing, but if you ask around in back channels, you may get lucky.