Every Live Photo is really two files: the picture, plus a 3-second video clip. That clip is often larger than the photo itself. Keepmemory removes only the video and keeps the still — same resolution, same date, same location, same albums.
Nothing is uploaded. Keepmemory has no account, no server, and no analytics. Your photos never leave your iPhone.
Photos you swipe left go to a review list. You see them all together before anything happens, and you can pull any of them back out. Deletion happens once, at your confirmation, and everything lands in Recently Deleted for 30 days.