Module uses four ways to translate their string:
1. Module translation csv
2. Translation Packages
3. Theme translation csv
4. Database translation
There priority is from top to bottom. So if your theme and your module both contain the translation of “Add to Cart”, your theme translation is applied. You can check the order of translation applied in file : https://github.com/magento/magento2/blob/2.3.2/lib/internal/Magento/Framework/Translate.php#L198 here the order of translation is :
$this->_loadModuleTranslation();
$this->_loadPackTranslation();
$this->_loadThemeTranslation();
$this->_loadDbTranslation();
So you can easily add those string in your theme and it will override your module translation.
If you remove those csv file from third party extension, you need to check every time when you upgrade those extension. So the better option is to add those translation to your theme.
I hope it will help you!