Should we use "Send Message Event" or "Sub-Process Activity"

# Child Process Count is around 300. I want to Hold my process execution based on my CDT field and then it will create no of instances based on payload (Max 300).

# is it possible to change hold time on the fly. I searched and came to know that to edit constant on the fly I need to use plugin which I cant use.

Attached : process model.

Kindly give you valuable Advice..

# Child Process Count is around 300. I want to Hold my process execution based on my CDT field and then it will create no of instances based on payload (Max 300).

# is it possible to change hold time on the fly. I searched and came to know that to edit constant on the fly I need to use plugin which I cant use.

Attached : process model.

Kindly give you valuable Advice..