unnieeee~ I'm doing fine! you know struggling with life in general. as usual.
personally I feel that the teen top fandom is not very active in the fanfiction community (as you can probably see from the lack of new teen top stories and story updates whether it's on aff or somewhere else) but I think you can find the fandom more here on aff and livejournal.
I've never been on Ao3 and have rarely sighted kpop fics on fanfiction.net.
livejournal has some amazing quality fics but I find it kind of hard to navigate through and can get confusing and even messy at times. this is one of the reasons I have been keeping to aff only instead of posting my fics elsewhere.
personally, I'm not a fan of wattpad. only like the fact that they have an app.
I don't know, I'm probably biased but I have a certain attachment for aff, all the people here, the readers the writers. probably why I stuck around so long haha

Livejournal is super confusing at first. It's probably easy to get when you know, but man, I struggle, lmao. But what omgith says - the quality of fics on lj exceeds what you find elsewhere. AO3 is having good kpop fics as well though I've never tried posting. I would use AO3, I think ^^'
Wattpad to me is something I associate with plagiarism and bad writers. I wouldn't choose that ever.
I have no experience with fanfiction.net

Blah! I wish we could edit posts, but anyway!
Archive of Our Own also has super high quality fanfics! I've noticed they tend to be really angsty on there?! It's strange! But I think the website is very nice and lovely!

well I know wattpad... it's quite popular but there aren't that many kpopfanfics yet...
it's nice for your readers though because they can keep reading even if they don't have internet! I don't know how to see how many people subscribed to your story though and that annoyed me... :/

Livejournal is confusing at first, but after you learn the ropes, it's very easy! It has the highest quality of fanfics of all the websites, for some reason! (I mean, a lot of people mention it, not just me XD.) And it has a LOT of Kpop fanfics on it!
Wattpad is easy to use, but you have to upload a picture with every story, I think? So make sure ya get that done! :3. I'm not sure how many Kpop fanfics are on it, since I don't really use it.
Fanfiction.net doesn't have a lot of Kpop stories on it. I'd recommend doing that one last^^

Ao3 has a huge fanbase for teentop, as far as i know, since i've also been on there. However, the wattpad editor i equally as good too.
amongst fans wattpad is probably more popular(i even downloaded it) though i'm not sure since im lonely XD <3

I'm Teen Top fan : D CHANGJO <3