Apps that move to a SD card are very few. So the only way to have other apps (most) on the card would be if the card had been converted into "Internal" rather than "External" storage. If that is done, then you would be moving the apps, no reason to delete.
With the photos, or other files, you shouldn't have copies on the phone's storage, unless you copied them rather than moving them.
Now in regard to where to find, I am a tad confused. Items on the card are already 'downloaded' as they are on the card. If you are wanting to view an image, play a music file, etc., then you would have to open the app you are going to view/play it in and make sure that apps settings are set to look for the items on the SD card. Now if the card was converted to "Internal" storage, that wouldn't be necessary.