120^2 mm radiator+fan on the M22, 140^2 mm radiator+fan on X42/X43/Z43. This has drastic effects on the cooling performance. Typical chip cooling capacities are around 35W (Athlon 3000G) 65W (Ryzen 3600) 95W (Ryzen 3700X) 125W (Intel 10700K) or 250W for something like a Threadripper. Regardless of the brand and the fans, 140mm radiators are generally a little tight for more than 65W of waste heat, the 120mm radiators are then only suitable as a cooling solution for the low-power chips.

An additional, more cosmetic difference is that the M22 has the pump built into the radiator instead of the CPU cooling block, as is the case with the X and Z series.

The M22 is for 120mm fans, this one is for 140mm fans. (slightly larger)