Best practices on how to combine HR data from other non Oracle applications with Oracle Cloud

Summary:

I would like to know how other customers have linked data from other applications to their Oracle cloud solution. we have OAC and use ADW as a data source and also generate OTBI reports from Oracle Cloud HCM. But we have a number of other non Oracle applications where we manually combine the data or use another 3rd party tool to hold and combine the data. I know that we can either load the data into ADW or use OAC to connect to other sources but want to know what other people have done and what works well or does