Hi,
I will recommend you to use variants but for the interface you want, it will require some custom developments.
You can have to "add to cart" buttons in a product listing or in a product page. To do that, you must make some modifications in your HikaShop store (using view overrides, nothing to modify in the core).
When you display a product listing or a product page, the related products are not loaded, so you can't display them like that.
That's why you have to put a specific module for the listing of related products.
Regards,
Jerome - Obsidev.com
HikaMarket & HikaSerial developer / HikaShop core dev team.
Also helping the HikaShop support team when having some time or couldn't sleep.
By the way, do not send me private message, use the "contact us" form instead.