Hi,
1. Yes, hiding the area with CSS is fine.
Removing the No can be done for the option itself (not for all the options) by adding a characteristic with only one value to the option product and having only one variant.
And if you want to hide the options ara only for some products, then you need to make your CSS smarter.
For example:
#hikashop_product_PKG20000_page #hikashop_product_options{ display:none; }
will only hide the options for that one product.
2. Displaying the add to cart button there even if the product has options is quite easy by editing the file "quantity" and adding such code at the top:
unset($this->row->has_options);
However, that will just result in the product being added to the cart without the options.
Adding the options with it on the listing will be much more complex as the options are not loaded at all on the listings. You would have to add custom MySQL queries and PHP code to load the options and add hidden input fields to handle that. That would be quite complex.