Conditional fields on content type with paragraphs
Yes you will have to hook form alter.
Make sure that you have done the following to make sure it's working.
1- create a module say it's called deals
2- add the deals_form_alter(...add the default params here ) In the deals.module file.
3- clear the cache 
4- add your edit form is in an if condition then right the following logic. (You can get the form is by dumping the $form['#id'].
5- use the states functionality or Ajax callback to hide and show the fields you want.

https://www.drupal.org/docs/8/api/form-api/conditional-form-fields
And https://www.drupal.org/docs/8/api/javascript-api/ajax-forms