It should be possible to use Custom Marketing Forms on Events that require a Pass. Currently, if you use Passes on Events, it hides the function to use Custom Marketing Forms. Out of the box, you only have First Name, Last Name and Email Address on the Form.

You can use Custom Registration Fields in this scenario, however, these have zero relationship with the Contact record. If you wanted to use a standard field on the Form e.g. Address: Street 1 you can't do this, you have to use a Custom Registration Field or build a Power Automate flow as a workaround.

Customisation of an Event Portal and the Form which people submit when they register, particularly for a Paid Event should be standard.