How does KJ-600's capability compare with American counterparts(E2)?
Generally speaking, we have no idea. But from some reputable sources on Chinese social media, it would seem that they think KJ-600 went with what is basically E-2D's radar design, i.e, a UHF-band radar with rotating 18-channel (9 on each side) yagi antennas. It makes sense to do this because UHF band works better in detecting LO targets (AGM-158C for example), yagi antennas are chosen to increase gain for UHF signals and the radar mechanically rotates to complement yagi antennas' weakness in wide-angle scans. Sacrificing precision and data rate is acceptable because there are a bunch of gigantic high-power AESAs in the fleet, carrierbrone AWACS only really need to know where threats roughly are coming from. I think it's safe to assume that KJ-600 basically is on par with E-2D given China's reputable expertise in radar and AEWC design.