I capture files in RAW and fine JPEG. When batch converting to TIFF there are no problems but converting to JPEG results in hideous jaggies. Do I need to change any of the settings? Quality is set to maximum and ppi to 300.
Your settings are perfectly fine. I suspect the jaggies are caused by the software you're using to view the JPEGs. For example, Windows Fax and Image Viewer uses a very basic down-sampling algorithm.
Which image viewer are you using, and is it the same for both TIFFs and JPEGs?
Try viewing them at 100%, and the jaggies should disappear.