The "Publish to Email transformation" uses ODS HTML to generate the output so you'll get a HTML output. If you want an XLS output then there is a way. You could change the extension of the output file to xls to generate xls file from the ODS HTML. This is an old way of generating xls from ODS HTML.
Now coming to the SPK file. This is something you should look into. Since you are looking into getting an xls/csv attachement which you can open and do some manipulation etc. SPK file is like a ZIP file. You can right click and unzip spk file. Basically you can put in all your files within a archive/spk file and get that emailed as attachement using the "Publish to Email Transformation"
To get this done, go to the properties of the "Publish to Email Transformation" and Under Publishing option=>
- select Send report in an archive (.spk) file as an email attachment in the Select viewer file/attachment option field
- provide folder/path where the spk file would be stored under Select path of where to store archive file containing report
- provide the name of the spk file under Specify filename of archive file containing report
- provide name=value pair of the package under Specify one or more desired package name/value pairs for package. For example this transformation is generating a PROC PRINT of an INPUT data set and the output file is c:\sushil\test.html then enter myname=(test.html) . The myname is for labeling purpose when you unzip the spk you should get test.html
Now Under REPORT SPECIFICATION option in the "Publish to Email Transformation" transformation select "Generate PROC PRINT from input table" and then enter the path and filename of generated report which based on our previous entry should be c:\sushil\test.html
Also, to select "Generate PROC PRINT from input table" you would need to right click the "Publish to Email Transformation" and select Ports -> Add Input Port. This how you can connect a table with the transformation. Now this is the minimum settings required to generate spk package from the transformation. Let me know if it helps!!
Note: This information is as per SAS DI Studio 4.6. I don't know if the transformation is updated in the newer version of DI Studio.