Is there any limitation on Package size and number of machines for deployment in client automation?
CA Client Automation - All supported versions.
There are no documented file limits for the Software Delivery module. However, the OS might have some restrictions on maximum file sizes. In addition, network bandwidth might impact the ability to deliver large ITCM Software Packages.
ITCM clients have packaged and delivered Software packages with 80GB files (VMware images) without any problem.
When its comes to current deployment and Future deployment numbers as per your planning, First point to consider here is network bandwidth between domain manager and agent machines. Points to check