Kangnam, as I understand it, is best known for poor quality pirated versions of other folks kits.
You can be sure that their 1/48 F-111 is a knockoff of one of the Academy kits and their 1/48 A-10 is likely a knockoff of either the Monogram or Tamiya offering.
I've seen their 1/48 SU-27 in the box and it is Academy's kit and a very poor copy of it at that.
I've heard very few people say anything good about Kangnam kits