Hi Vara,
Are you using foundation adaptive form or core component based adaptive form? In both the cases, a theme is applied at the form level only. A form can't have two themes applied. For your use case, you can consider the following approaches
Foundation Adaptive Form
You can define a class name for a table component within an adaptive form. Define styles with table class name as parent selector for components to be used within this table. The CSS styles can be defined in a CSS file or client library and can be applied to form, so these specific styling apart from theme can be picked.
Core Component Adaptive Form
In this case, you can leverage style system framework to define different style variant for a component. In authoring, you can chose variant to be applied.
Regards,
Pankaj Parashar