@AbhishekC1725 Any associate node is used most of the time. There are few pega ootb job schedulers that runs on all nodes. Eg:- node cleaner, and some other cleaner job schedulers. Those job schedulers run on all nodes to process on all the nodes. If we need to do some processing on all the nodes, then we can use run on all the nodes and if we want faster processing also we can use run on all nodes. But if we are running on all nodes for faster processing we need to make sure that cluster is healthy, else same processing(activity) will be running a duplication on same records as nodes will not be able to communicate.
Run on any associate node is the one which mostly used. In this job scheduler will execute activity only on any one node.