Happy to help!
One thing I did not mention in my solution was to make 100% sure that you exclude any PII in the form data from being collected by Google Analytics.
Since we’re talking about appending the data to the URL via a query string - GA will automatically capture that data inside its pageview reports. This means you’ll likely need to add some custom logic around your tracking to make sure you adhere to the GA terms of use regarding collection of PII.
If you’re using GTM (Google Tag Manager) to implement your web tracking (if you aren’t I highly suggest you investigate) - this article is a great resource for understanding how to exclude data from being collected:
Simo Ahava’s blog
#GTMTips: Remove PII From Google Analytics Hits
Use customTask to automatically strip all personally identifiable information (PII) from requests sent to Google Analytics from your website.