There are very few themes that are incompatible with Product
1) Product Page
Most themes and cart pages will work just fine with the app. However, some themes have the ability to use “drawer”-style carts in your store. These drawer carts will not work with products whose options have costs associated with them; drawer carts to do not refresh the page when updating, and thus will not correctly apply pricing changes when product quantities are updated.(This could cause incorrect order totals with personalization.) Please view our document on drawer carts to see which themes have these cart types, and how to disable it.
2) Cart page
If the theme become incompatible for cart page it is suggested to Set create new product when saving personalized image . Details here..
In a ideal cart page there should have no ajax functionality which prevent refreshing cart page.(This could cause incorrect order totals with personalization when updating quantity.)
For updating quantity there should not have any plus / minus button . There should have an update button also.
Here is an ideal cart page sample