iOS 8 seems faster on my iPhone 5, around the same on my Mini 2 and after a clean install and restore in iTunes, around the same if not a little slower on my iPad 2.
Videos I've seen of the 4S on 8.4 would indicate almost identical performance, and since the Touch 5 is so similar, the same thing should happen (though the video was of a clean install of both iOS 8.3 and 8.4)