A subnet can have only one NSG

A NIC can have zero or one NSG

Inbound rules of an NSG associated with a subnet have precedence over an NSG associated with the VM’s NIC

For outbound rules, however, it is the other way around the rule on the NIC takes precedence over the rule on the subnet

If you have several network security groups and are not sure which security rules are applied, you can use the Effective security rules link in the Azure portal. You can use the link to check which security rules are applied to your vms, subnets and network interfaces.