So I am confused, How Much is Bitcoin Address with balance today?,

As I know, we can create unlimited Bitcoin addresses using a 12/24 word mnemonic seed and put the balance in multiple of addresses. But not all people spread it to another address, usually sent to the same address if want to save it. I think it's very dangerous and will be a target. everything is gone without a trace.

Another question, Is there any method to check Bitcoin address was created and filled in the balance?