Personally I always shoot RAW and save the processed file as a jpeg, usually up to about 3MB (hope I haven't misunderstood the OP's original post). Naturally I save the RAW files (they're the 'negatives', after all). The only time I use TIFFs is if I've scanned an old photograph and want to work on it over a period of days or weeks, eventually saving the finished image as a jpeg. I usually retain the original TIFF file, plus one or two of the most recent TIFFs relating to that image, depending on whether I may want to revisit an adjustment.
If I've used any perspective adjustment in PSE then, when I come to save it, the default option comes up as PSD, but I always select the jpeg option at that point because by then I'm usually done.