This is really going to depend on what you need from your AKS clusters. Both options are viable, option 1 will be more expensive as you are duplicating resources for running things like Ingress that potentially could be shared between productions, but it will provide more flexibility. Similarly, if you think some products will need a very high node count, or have different requirements for upgrades etc. then you may want to put them on their own cluster.
You could also look at a third option, which is to use a single AKS cluster, but with Node Pools per product. That way you can isolate each product in their own node pool, and specify different node configurations per product.
Ultimately none of these are incorrect, you need to consider what is more important, cost or flexibility.