Hello,
The main point in your question, is here :
" two slider with related products, one for the category A and one for the category B"
There is only 2 possibilies :
=> in your module, either you display related product define in the product configuration page itself
Or you display different category, that you can define in your module, in HikaShop Options tab :
But you can't have both, I mean Related product sort per category, so maybe I didn't understand you well, then please provide more elements, or I understood you well, and I'm afraid that what you request isn't possible.
Awaiting more elements from you.
Regards