Confused with my master password and account password

So my account password is also my master password? On my computer my master password unlocks both my vaults. Both my vaults then sync with the web account and I can view those with my account password on the web. So if I had an old vault which the old master password unlocks, shouldn’t I not be able to see it on the web when I login with my account one?

Or do you mean my master password unlocks my local stored vault (nothing to with web account) and the fact it syncs means then I can see it on the web with my account password (so nothing to do with local password). And that means my data on the web can’t be encrypted with my master password. Is it encrypted with the account password? If so, how does it sync data between two different password encryptions?

Maybe I just change my account password to the same as my master one, and even if there are two separate ones used at least it’s the same password I remember and type in.

Thanks