Hi,
To remove the add to cart button and quantity field on the product page for products in a specific category it will require view override.
The view to edit is "product / show_default" and you can replace the code:
<div id="hikashop_product_quantity_main" class="hikashop_product_quantity_main">
<?php
//LAYOUT quantity
$this->row = & $this->element;
$this->ajax = 'if(hikashopCheckChangeForm(\'item\',\'hikashop_product_form\')){ return hikashopModifyQuantity(\'' . $this->row->product_id . '\',field,1' . $form . ',\'cart\'); } else { return false; }';
$this->setLayout('quantity');
echo $this->loadTemplate();
?>
</div>
By:
<?php if(!in_array($this->element->product_category_id,array('XX','YY'))){ ?>
<div id="hikashop_product_quantity_main" class="hikashop_product_quantity_main">
<?php
//LAYOUT quantity
$this->row = & $this->element;
$this->ajax = 'if(hikashopCheckChangeForm(\'item\',\'hikashop_product_form\')){ return hikashopModifyQuantity(\'' . $this->row->product_id . '\',field,1' . $form . ',\'cart\'); } else { return false; }';
$this->setLayout('quantity');
echo $this->loadTemplate();
?>
</div>
<?php } ?>
And replace 'XX' and 'YY' by the desired category ids.