There are two ways in which you can limit which options are available to your users:
Limit select options in general
This feature can be found in the advanced section of the single and multiple-select fields. Here you can choose the options that people can select from under Limit selection to specific options.
This will hide the options from the miniExtensions form but still keep the options in Airtable to not lose the contextual data. It just limits the drop-down options in the single or multi-select fields.
Limit select options conditionally
You may also wish to limit which options are shown based on certain conditions, e.g. when another field contains a certain value. You can do so in the Show options conditionally section of your field's settings.
The feature outlined above overrides this setting, so if the option is hidden in general, this feature will not show it.