Explanation:
Graphical user interface, text, application Description automatically generated

Box 1: Yes
The four columns used in the 2018 transactions are already displayed.
Box 2: Yes
The columns used are based on the entire dataset. The additional columns in the 2019 files will be detected.
Box 3: Yes
Note: Under the hoods, Power BI will automatically detect which delimiter to use, and may even promote the first row as headers. You can manually change the delimiter, or define how Power BI should handle data types. You can set it to automatically detect data types based on first 200 rows, or the entire dataset or you can even opt out the detection of data types.