In the Other Settings tab, you can find two important options for hiding the product prices and the Add to Cart button.
You can hide one or both of them on all the products in your shop, so, you will be able to show only the Quote button and to let your users submit a quote request.
Go to YITH Plugins > Request a Quote > Other settings and check the right option(s), based on your own needs.
Please, consider that these options remove the price and the Add to Cart button on all products.
If you need to remove these on some specific products only, please, consider the integration with YITH WooCommerce Catalog Mode plugin.