Hi Brad,
I added code in method 1 and didn't encounter your issue, my test marketing page is hosted with system.
> You should authenticate your domain in settings if you host form on external server to enable prefilling feature.
> As per my understanding, you would like to make remembered contacts can't edit their information again after they checked Remember me option?
> However, input fields prefilling feature is controlled by cookies, the cookies data will be stored on contact's side machine after form being submitted, we can't detect/monitor this behavior.
In my opinion, read only input field is more compatible with subscription center form.
> Event website is built with Angular framework, I'm not an Angular developer unfortunately, please read this doc to make customization for event page.
Regards,
Clofly