How can I uninstall the app or cancel the plan?

For dummy products and variants:

You can delete the bundles on the BYOB dashboard. The corresponding products will be deleted

For template files in your theme:

You can find the below files from your theme (search. There are:

1 product template:

byob.json
other templates created by you

2 section files:

byob-custom-messages.liquid
byob-empty-state-hint.liquid

1 snippet file:

byob-messages.liquid

The section files below are not available if you are using the latest theme app extension (TAE). Skip them if using TAE (Install the app after March 2023).

7 section files:

byob-bundle-info.liquid
byob-confirm-modal.liquid
byob-product-grid.liquid
byob-footer.liquid
byob-quickview.liquid
byob-subscription.liquid
byob-reviews.liquid

How to delete the app?

To cancel your BYOB plan, go to your Shopify admin, navigate to the 'Apps' section, and locate the BYOB app. From there, you can uninstall the app to effectively cancel your subscription.

Your app charge

Once you delete the app, your account will not be billed for the next billing cycle of the app subscription. Please check the billing cycle dates of BYOB as apps don't follow the same billing cycle as your Shopify subscription. Apps will follow a billing cycle based on the date that you install the app.

Everything about working with apps: https://help.shopify.com/en/manual/apps/working-with-apps

About your app subscription charges: https://help.shopify.com/en/manual/your-account/manage-billing/your-invoice/apps#subscriptions