I'm trying to do some theme optimisations as I'm finding a lot of significant issues with Shopify's overall performance and the more apps I have to add to fill functionality gaps the more extreme it gets.
Is there a way to simply disable an app without deleting it completely so I can test performance? It seems a little unusual that the only option is to completely delete an app.
If it's an app that works based on code in your theme, you can comment out that code.
If it's an app that injects code into theme via content_for_header, you can use some liquid code to identify the url and assign a new content_for_header with the app script removed.
If you're not comfortable working in the code, you can either hire a Shopify developer or contact the app developers to ask if they can give detailed instructions how to temporarily disable the app.