If you are planning on overclocking a Ryzen 2700x which has a TDP Wattage of 105 Watts it will be best, in my opinion, to get a high quality high wattage Liquid Cooler to maintain below its maximum Operating Temperature of 85c degrees.
Also remember if your Ryzen gets damaged, by overclocking, AMD Warranty is voided. Also if you do a incorrect Overclocking it will cause you computer to become unstable by crashing or BSODs.
Here is AMD Recommended Liquid Coolers for Ryzen Threadrippers: Thermal Solutions for Ryzen™ Threadripper™ Processors | AMD
Well I can tell you that with my 1800X, under full core extended stress, such as when encoding a video, running at 4ghz, with my Corsair H115i, it runs at about 60*C, and I would highly recommend it if your case can fit the radiator as under gaming loads it's dead quiet thanks to its cooling ability. You can also go with the Corsair H80i V2 for a little less money, or with an air cooler for even less money, but since AMD is likely to continue to use the same type of socket in the future, going with a high end closed loop liquid cooler is an excellent investment.