Azure - Traffic between two Virtual Networks or between two Address Spaces same Virtual Network

We have a Virtual Network with a single subnet that covers the entire Address Space. AKS is running on this Virtual Network. We want to assign internal IPs to resources such as CosmosDB, SQL Server, Virtual Machines, etc. There are two options we are considering:

The first is to add a new Address Space to the existing Virtual Network. Divide it into subnets (one for CosmosDB, another for SQL, another for VMs…). This way, pods accessing these resources do not leave their Virtual Network.

The second option is to create another Virtual Network with a new address space and make the same subnet division. In this case, pods that need to access resources leave their Virtual Network through the Azure backbone.

We have a question: does communication between different address spaces in a Virtual Network also go through the backbone and is it direct communication within the same network? We want to avoid constant traffic through the backbone between services and resources that are working together.

Thanks!