aws cloudformation for atomic stack-update

I have a stack consisting of
ec2 instances as an application server
one ELB as a load balancer
two Elasticsearch nodes
If I update the stack for whatever reason, perhaps to increase the number of application servers, all new components are ready to handle my current stack and my current stack is replaced by the new one at the same time, like atomic operations in database systems?

Since this reduction involves the desharding of existing data in Elasticsearch, does the same procedure also apply if I reduce the number of Elasticsearch nodes?