CLCs are are basically the same unit. They all use similar, cheap pumps along with basic radiators and tend to mix metals.
An open loop cooler is just that, open. You can put another res, rad, waterblock, whatever in it that you want. Examples are like the H240x2 or the EKWB predator series.
One of the best thing you can do for an AIO is to replace whatever fans come on it, especially a corsair cooler.