Generally, you can use any 3rd party plugin with the theme, without custom integration. But the integration makes a plugin tightly coupled with the theme by adjusting a variety of its aspects, the same turning the plugin into an internal part of the theme.
A plugin integration covers:
- custom styling
- placing plugin-related elements inside theme templates
- including plugin-related query arguments in the filtering and sorting
- adding builder blocks
- integration with other theme plugins
The theme is not responsible for plugin-related issues. If you encounter a problem and a plugin is not working, please first check whether the same problem occurs on the WordPress default theme. If so, you have to report it directly to the plugin author.