RE: Email Validation on Landing Page
Hi Mike,
You could create a new form field record, taking the Email Address 2 field of Contact as the 2nd email field for verification.

Custom validation can be added to form with form API:
At formSubmit event, check whether value of Email is equal to value of the 2nd email field, if yes, allow submission;
if not, prevent submission and show an alert with error message to contacts.
1. In form editor, set both of email fields to be required.
2. Go live the landing page which is embedded with marketing form, get the id value of two email fields with inspector.(F12)

3. Stop the live page, add following validation code after end tag of body, nest code in script tag.
Replace id in sample code with your owns.

MsCrmMkt.MsCrmFormLoader.on('formSubmit', function (event) {
var verifyEmail = document.getElementById('frm24da2d4af-3e08-eb11-a813-000d3aa08990').value;
var email = document.getElementById('frm2e1dfc514-f301-4cb2-855a-4c8fa8331207').value;
if (verifyEmail !== email) {
event.preventDefault();
alert("Make sure that the value of 'Email' is equal to the value of 'Verify your email'.");
}
});
Result:
Contact will receive an error message if value of two fields are not equal.

Regards,
Clofly