This helped a ton for me, I opened a second savings account for travel/vacation savings and I have thought about opening another checking to separate “fun” money from expenses money.
Some banks make it really easy, where you can freely create sub-accounts for each bucket of money, but it seems like a majority make you apply for each account. In my experience, the application gets instantly approved, but it makes it seem harder and scarier than it really should be.
Keep in mind that the sub count you see is the number of subscribers from your instance. I see 9.3k from my lemmy.world account, 250ish from my lemmy.ml account, and 300ish from my lemm.ee account.
Not sure how/where OP sees 12k though.