All AmEx account downloads renamed to clothing category

The account itself shouldn't have anything to do with categorization; Quicken Mac looks only at the Payee name; if you make a purchase from Amazon in the Amex account and Amazon in a different credit card account, the results should be the same.

Renaming rules are to help you drive Quicken to use a consistent Payee name. Some transactions download like "Home Depot Store#1234 Anytown", and a renaming rule can change that downloaded Payee to "Home Depot". Renaming rules don't affect the category, just the Payee name.

QuickFill rules allow the category, or all fields, to be filled in when a transaction for an existing Payee is entered or downloaded.

It used to be that the next level of attempting to categorize a transaction would depend on whether the Payee has an exiting transaction in your database; Quicken would simply apply the same category as the most recent transaction for the same Payee. If Talbots is always clothing, this worked great; if Home Depot is sometimes Lawn & Garden, sometime Home Supplies and sometimes Tools, then new transactions would just be whatever was used last since Quicken doesn't know what you bought. This is the way Quicken Mac worked prior to QuickFill rules. It does not do this any longer for manually entered transactions; I'm not sure about downloaded transactions with no QuickFill rule.

When there is no QuickFill rule to specify the category for a Payee, Quicken attempts to categorize the Payee based on a database of crowd-sourced data. It might know that Exxon is gas and Talbots is clothing. These server-driven results can be helpful, or can be off the mark. Some people find them incorrect often enough that they turn off the Preferences > Connected Services option to "Automatically improve the quality of downloaded payee names and categories". That turns off Quicken's attempt to clean up payee names and to auto categorize transaction, so it might leave you with a lot of "Uncategorized" transactions instead of some correctly and some incorrectly categorized transactions. But some people prefer this so they can search for Uncategorized transactions and categorize them manually. Also, note that this auto-categorization only works for the categories Quicken starts with as its defaults; if you create a new category, Quicken's crowd-sourced categories will never match with your own category.

All that said, my suggestion is that you create a few QuickFill rules for specific Payees you're finding mis-categorized currently. This can be done quite quickly: if you've corrected a transaction to the category you want it to use, you can select Transactions > Save a QuickFill Rule (or Command-Y), and Quicken will create a QuickFill rule matching that Payee to the Category of that transaction. The next time one of these Payees is used in a downloaded transaction, it should apply the category you've told it to. Once you find this works, you may want to spend a little time building your library of QuickFill rules for recurring Payees.