Overwriting templates is an easy way of customization. You can easily overwrite templates of Addonify Floating Cart plugin.
In the Addonify Floating Cart plugin, you can find the front end templates inside public/templates folder.
To overwrite the plugin templates, create a folder, addonify/floating-cart/, inside your parent or child theme folder and then create PHP templates with similar file names, as in the plugin, inside the folder.
Write custom codes in your template files according to your requirements.
Once done, the templates you have overwritten will be loaded from your theme rather than the plugin.
Have fun 🥂