Hello, I'm sure i have answered this somewhere else but basically, Ragexe, RagexeRE, Ragexe_zero these are the client releases used on the official Korean servers in general there is few user interface differences and few features that may exist in one and not the others but eventually all of them get the features in later releases. as for Hercules I'd suggest the use of Ragexe or Ragexe_zero (zero only if you want something that exist in it..) because those are the main servers (RagexeRE are for a test server so some features can be broken in early versions) last thing your server build (pre-re or re) doesn't matter to the client you can run any version for any build you want.
for nemo fork secret's one is discontinued you can use this instead: https://gitlab.com/4144/Nemo