How to create an upsert dataflow?

Situation:

• Source data needs to be upserted into a destination table. 
• Prefer to use only Power Bi/ Power Platform SaaS tools 
• Prefer to avoid using Azure services
• Prefer wysiwyg tools
• I can pull the data from the source system using the existing text/csv connector. 
• I expect that I will need to use one or two dataflows and I am comfortable with recurring schedules. If two dataflows are needed, I hope the second one will run automatically after the first one is done. 
• I am building this in a brand new account/environment
• I am fine if this is done using the new datamart features

Problem:

• I am inexperienced with how the Power Platform tolls are "meant" to be used
• I would expect that I need to pull the data into a table, then run a dataflow that reads from the source table and destination table, then does the upsert and finally writes back into the destination table. I can't figure out how to do this. 
• I don't know what licenses/permissions I need to make sure I have all the necessary tools. I am fine paying for the MSFT services necessary to make this possible 

Goals

• Produce the "most simple" approach to get this upsert working within Power BI/Power Platform
• Prefer to use minimal license costs... simplicity takes priority.
• I need to understand what licenses/tools/permissions are needed
  • Power BI Premium? Power Platform Premium? Dataverse? Azure data lake?(seems this is where dataflows save data when set as Analytics type), ect.

How can I configure Power BI/Power platform to solve this upsert use-case?

I greatly appriciate help and guidence on the approach, tools, and steps needed to make this work as simply as possible.