With a hyper 212 evo? Not going to get too much of an OC. Realistically you're going to be trying for 3.9ghz or 4.0ghz with a ryzen cpu. Most of the 240/280/360 AIOs will be plenty for an OC like that and a custom loop will likely be overkill. For what it's worth I have a h115i that I'm getting rid of because the pump noise is driving me nuts. I'm going back to air cooling and I really think for these CPUs air cooling is plenty as long as you have a decent cooler, a hyper 212 is pretty entry level (I used to have one). Just keep in mind it's not necessarily the thermals that hold people back when trying to go over 4ghz on this chips. I'd highly suggest if you give a bigger air cooler a shot, it'll be cheaper, quieter, and more reliable than water (a big air cooler can still act as a passive cooler if something fails).
I'm not advising against water, there are obviously reasons to want it but I have a 1600x I'm still playing with to get a stable OC and the limiting factor hasn't been the thermals (not even close).