magento2 – Product page modification for specific products

I would like to make some product modifcations; change qty position to move in the top, add total price (qte* unit_price) in /vendor/magento/module-catalog/view/base/templates/product/price/amount/default.phtml.
The problem is that the block is modified in the catalog page also.
I need to make some change to the custom options block also.
So my question how to make those changes for specific products only (i can add a product attribute for that)
Thanks.