The process step can be expected as first step because when you run a workflow in transient mode AEM does not store any workflow history but when the transient workflow enters a participant step it changes mode (at runtime) to non-transient; as the task is being passed to a person the history needs to be persisted.
I was reading this doc: Developing and Extending Workflows
is there any benefit to marking a workflow as transient, if it does have a participant step, or it has an AND split (or any other condition that makes the workflow non-transient) ?
We are trying to decide if it's worth the hassle.
Additionally, it seems like no matter what, the initiator of a transient workflow will always be "workflow-service", is that the case? always?
I would go with transient if there is no user interaction like DAM Asset Upload workflow. If you are not sure whether to use transient or non-transient with user interaction you can go with non-transient.
The workflow purge tool can help you to get rid of workflow instances which created for non-transient workflow .