Hi Jason, I'm not an expert with code, but the advice from Bold Apps was that they would have to disable ajax add to cart, to install their app. I asked if it was possible to leave it on but just not have the options displaying in the ajax add to cart, while they would still appear on the /cart page, but they said even this was not possible.
Bold Apps mention this here on the app details page under important things to note
"AJAX add to cart functionality will need to be disabled to pass options through to the cart."
On a search for product customizer and ajax I found this page that essentially said the same thing
http://skyverge.github.io/fieldday/reign.html
"Important note about the Reign theme: The Product Customizer app is not compatible with the 'Ajax' feature of the Reign theme. This means that the Ajax Product feature must be turned off in your Theme Settings in order for the app to function properly."
I'm not sure about the technical details, but the upshot seems to be that they are not compatible, but I'd be grateful if you have any suggestions.