If you have this category-product tree:
product 1 - cat A, cat B, Cat C
product 2 - cat A, cat B, Cat D
And through carousel module parameters,if you set:
- carousel 1 - show cat C
- carousel 2 - show cat D
Carousel 1 will show only products that belong to Category C, so it won't show product 2 but will show product 1. Same idea for Carousel 2.
But if you create an another carousel module and set:
- carousel 3 - show cat A
Then carousel 3 will show product 1 and product 2.
Choosing "Random" doesn't mean, random from all categories. (if you set the "category filter" to YES). It should select the products from that specific category randomly. (instead of showing "only featured" products from that specific category, or only "new products" from that specific category). Also the "random" will let you have random sorting each time the page gets loaded.
Regards.
Support