For your alts do you need them or are you are just leveling them because you have them?

If you already have your main team then just use your alts for things like Manufacturing, collecting or as a shop. If that's to many chara to log then don't log them. If they are empty and under lvl 20 and you find they are not needed then trade all the good tradable items to another chara and delete the rest.

You can also just keep them as storage and later if you ever think "Hm I should make a new chara to do so-and-so for me" then you will already have some alts in storage already made. If you happen to hate their name then you can always delete them and remake them using the old account with a new name.

For now Just get a notebook and Write down all the accounts and passwords with the names of each chara so as not to forget them. (when done keep the note book in a safe place you can find but no one else can)

Write the 4 main you use as your team
1 you keep for manufacture

The top 5 can share other jobs like being a shop and even your manufacture if not doing anything can be a collector.

If you think it'll go faster to have separate collector and more space to have spate shops then do that. Make a note next to each account, such as; Fire killer, water, compounder, shop, stone collector, wood collector, jade collector, extra storage 1, extra storage 2, etc....

You do not need to log in every chara you have just because you make them. (I have 9 and I even went and rb'd them all because I didn't want any of them to be left out and believe me when I say I wish I never had that many because I cannot use them all and I always never know what I should log in and for what in the end I have to abandon 5 and keep 4 for my main team. yet I still continue to lvl them so they all stay same lvl range now I feel its a chore and I just don't log anymore and the game is no longer fun)