Can I use dataflows in this scenario?

hi DeBIe ,

If all of the data is teh saem - but only broken down by customer then my thinking is that you do all of the data and as much of the ETL as you can in the dataflow.  Dataflows can be quite powerful and I use them all of the time (here is an articl with some "when to use" information) Introduction to dataflows and self-service data prep - Power BI | Microsoft Learn.  

Once you have your dataflow as close as you can get it to the final result I would then create a desktop report that usess the Dataflow and I would creates any additional ETL type functions in that file that I could not do in Dataflow.  This allows the "heavy lift" to be in the Dataflow.

Finally, I would use RLS to differentiate between my customers as much as I could.  That way I don't have to have multiple reports. After setting up the RLS that should allow you to have a very few number of reports (hopefully just one) to update and reconfigure as needed and then share to customers based on your RLS settings.