A few points to remember

The following are some noteworthy points to remember:

• Don't perform the DML operation inside the Loop element. It will easily hit the governor limit, that is, System.LimitException: Too many SOQL queries: 101.
• You can't refer to a Flow as Subflow if both types are not the same, refer to it as either Flow or Aautolaunched.
• You can only use the Wait element in Autolaunched Flow. 
• You can only launch Autolaunched Flow from the Process Builder. 
• A Flow runs in user mode and Process Builder runs in the system mode. Let's take an example if you are trying to update Opportunity the next step field:
  • If you use Process Builder: If the running user doesn't have access to the next step field, Process Builder will be able to update it.
  • If you use Flow: If the running user doesn't have access to the next step field, they will get an error.
• If the Flow doesn't have a Start element, you won't get a link to activate the Flow.
• The DML operation on a setup object is not permitted at the same...