Updating a Salesforce Opportunity record

In the Salesforce Integration documentation for Field mapping, it shows an example of how to Update a record instead of Creating a new one, and the key fields used in the example are First Name, Last Name and Email address, which is fine for Lead, Contact or Person Account, but what fields would be used to update an Opportunity where that data would would exist either through the Account look-up field (if Person Account) or through the related junction object Contact Role that connects to a Contact?

What I’m trying to do is email an existing Person Account a link to the Typeform which would then update one of their existing Opportunities.