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".
I'm just gonna go ahead and say it: 16 Characters are sufficient and 20 pretty damn secure.
That is assuming they do stuff right and there are no vulnerabilities, which they won't and there are. However they may manifest, they are a greater concern at 16+ characters, especially if they don't offer 2FA.
The reason is that even if machines become powerful enough that 16 characters can be bruteforced, which they can't atm, you can effectively defend everything against bruteforce attacks by other means. Including but not limited to limiting login attempts, salts and pepper, multiple encryption layers etc.
With just ~~a salt~~ pepper you can make a 16 char password effectively a 24 char password... Or a 2.000.000 char password. Assuming it is not stolen alongside that is.
Edit: Changed 'salt' to 'pepper'.
That's not how salt works. It will be stolen alongside the password hash, because salt is necessarily in plaintext. It doesn't increase the guessability of passwords. It just makes it infeasible to precompute your guesses.
So what does the password length matter if they also get the salt?
A password only 8 chars long can still be brute forced, salt or not.
Without salt, the attacker would make a guess, run the hash on the password, and compare it to the stored version.
With salt, the attacker would make a guess, combine it with the salt, and then run the hash and compare like before.
What salt does is prevent a shortcut. The attacker has a big list of passwords and their associated hash values. They grab the hash out of the leaked database, compare it to the list, and match it to the original plaintext. When the hashes have a salt, they would need to generate the list for every possible salt value. For a sufficiently long salt that's unique to each password entry, that list would be infeasible to generate, and infeasible to store even if you could.
If your passwords were long and random enough, then it's also infeasible to generate that list to cover everything. It really only works against dictionary words and variations (like "P4ssw0rD").