There is no split shipping in XC. So all your products have to use same shipping method.
I am not sure how this works in XC5 but in XC4 you can set free shipping for product and not account for its weight at checkout so shipping cost is only for the products that do not ship free.
There is this module -
https://market.x-cart.com/addons/shipping-per-product.html - but all product sin cart have to have common shipping method setup or checkout won't be allowed.