Not only does the credit bureau max out their password length, you have a small list of available non-alphanumeric characters you can use, and no spaces. Also you cannot used a plused email address, and it had an issue with my self hosted email alias, forcing me to use my gmail address.
Both Experian and transunion had no password length limitations, nor did they require my username be my email address.
Update: I have been unable to log into my account for the last 3 days now. Every time I try I get a page saying to call customer service. After a total of 2 hours on hold I finally found the issue, you cannot connect to Equifax using a VPN. In addition there is no option for 2FA (not even email or sms) and they will hang up on you if you push the issue of their security being lax. Their reasoning for lax security and no vpn usage is "well all of our other customers are okay with this".
This implies they're storing the plaintext password.
Ideally the password would be hashed with a salt and then stored. Then it's a fixed length field and it shouldn't matter how long the password is.
Salted passwords are not recommended anymore. Better to use a memory hard key derivation function designed for passwords, like Argon.
https://en.wikipedia.org/wiki/Argon2
Those are salted, they just do it for you.
Where does the salt get stored?
It's usually part of the string stored to the DB.
Edit: you can see the PHC spec here:
https://github.com/P-H-C/phc-string-format/blob/master/phc-sf-spec.md
Which is a common format for various password storage algorithms, including Argon2. It has a salt field.