what are you using the images for?
if you’re printing, i think that pretty much anything over 300 ppi is wasted.
if you change the ppi, be sure to change the dimensions as well, so your file size doesn’t change – that will help keep you from getting fuzziness or pixelation that would occur if you radically changed the file size.
example – my pics come off my camera at something like 48 x 32 inches, 72 ppi, which is about a 25 mb file (i’m estimating here). during my workflow i change the dimensions to 12 x 8 inches, 300 ppi, but my file size stays at 25 mbs.
ICC profiles are color profiles. if you have your workspace, your monitor, your camera, scanner, and your printer all set to the same profile, your prints/scans/files are going to be much more uniform from camera to monitor to printer (or whatever).