Using App Proxy to deliver custom content to user

Hello Shopify Experts,

Using a Shopify App Proxy allows to return Liquid, which allows to have user-level custom content. However, it requires to change the URL of pages. For example /collection/my-collection would become something like /a/c/collection/my-collection, in order to have a user-customed collection.

Can it be a good idea to display custom content to the users, for example through an app, or would it be rather damageable, especially regarding SEO?

Thanks