Power BI Performance Tables vs Flat Files

thanks... i have seen that article before.... Much of it reminds me of good database design prinsicples (ER Diagrams etec). The one area that talked about "performance" said

    * Wide Flat Tables = Poor Performance
    * Narrow Data Tables with separate Lookup Tables (Star Schema) = Improved Performance
I don't disagree, but have also learned in reality that depennding how the software is implemented.  It could be better performance wise to be flat. I have bene told Tableu does better with flat files and not relations.

My lookups in a relatin would remove some columlns, but would not reuce the number of rows my primary tables.

I guess I was curious if anyone had tested and done any simple comparisions on speed.

thanks for the response... if anyone has more detial would love to see it out of curiosity.

thanks

Alan