I experimented with image adjustments prior to stitching, but finally decided best to do the merge prior to any adjustments. Same concept, except you were doing it in the camera, while I was doing it after the fact.
if you shoot RAW, adjust before stitching, which lets you do additional exposure matching, fix color balance shift and other stuff. The merge is the last thing you want to do. ICE is a much easier to use application, but it forces you to open JPEGs, which makes only sense when you are shooting what your camera manufacturer's code monkeys figured would be a "good average" processing of the raw image. Most of the time that's junk, and once it is junk, you can't do much to fix that, as a JPEG is only a fraction of the original data recorded by the sensor.
If you want to make sure everything is in focus in a panorama, shoot manual focus, and if there is not enough depth of field, stack each frame with multiple different focus shots (google focus stacking). Then you have to stack each frame before you merge them into a panorama. Gets really tricky to track what's what, and that's definitely not something you'd do without tripod and a lot of time for a single image stitch. Gets real geeky at that point, so much so that I never did that myself. I've done stacks and stitches, but never stitched multiple stacks