My preferred method for password generation is passphrase, but I am always foiled by websites requiring a maximum password length that varies from 20 digits max to 128 digits max.
I would like my passphrase and limit total digits to whatever limit the password field has set. If I have 20 words in my passphrase, I would want shorter words to fit the length set as well. Possibly include longer words if a password length is set as well. To get over having to many words for the character length, possibly automatically reduce the number of words set to match the character length set.
Example: 20 words in passphrase, password field limited to 20 characters. Total words would be reduced to 4 from 20 when character limit is entered.