Niagara is amazing. It's quite different from other launchers, so either it works for you or doesn't. It perfectly matches what I was doing before, which was searching for apps by name to launch them.
Haven't tried KISS, just looked at screenshots. Niagara tries to be slightly customizable and aesthetically pleasing. I've been using (and paying for) it for years. Its plenty lightweight to be snappy on even older model phones.