I began by creating a text input that represents the join type:
And then a separate list of all join types:
This I applied to a drop-down list which actioned the first file to update the value with the value selected:
I then appended this to the two input files:
I then placed a join tool to join them together on the key field:
Each output combination was taken to represent each join type accordingly:
I then unioned the outputs of all joins, applied a filter to only show records that matched the join type and output as HTML:
This will output only those records that are the result of the join type selected in the dropdown.