We don't have to wonder, performance was measured in the review above. It is pretty much equivalent to all of the other CLC/AIO coolers. Of note the review used an 8700K, so if the there is something about a larger volume of cooler which will make more difference with a Zen2 than an 8700K (thinking of the concentration of of heat to a smaller surface area). Also you can note that testing was done at 100% fan speed rather than noise normalized.
If you like it then go for it, there's nothing to worry about, it has some added features compared to other CLCs (although it is not the only expandable all copper CLC available either). Just don't believe it will be a custom loop in a box.
Pump flow and performance is a pretty in depth issue and it does vary from loop to loop.