Different end points available in AEM workflow as Adobe Livecycle like watch folder, email etc

You need to manually code these yourself now using the AEM APIs and other APIs available to you. For email startpoint you would need to write your own SMTP inbox watcher using Quartz or other scheduler that would then launch an AEM Workflow once some patterns are matched and data is retrieved.

Should you have AEM Forms Workflow license, you have AEM Forms 6.0 JEE which includes the old Livecycle foundation components. This would enable you to set an email startpoint in a process to then communicate back to AEM but this could get a bit hacky.

AEM Forms 6.1 will re-introduce the concept of Watched Folders under AEM Forms but that will not arrive until full GA release of 6.1 (unless you are part of the Beta program)