Yes, the files of the Russian translation of mods BEFORE starting iconv should be encoded 1251. If the iconv does not start (as was the case in this case), then BG2:EE cannot start (there is no reaction to the launcher), because to start the version of EE, conversion to UTF-8 is needed. And the mod in this case will only work on the old (vanilla) version of the game. This problem was already with many Russian players with several mods, where the transcoder did not work.
And if you just put the translation files in the UTF-8 encoding right away into the folder, then BG2:EE its version of the game will work, but the old (vanilla) version of the game will not work (either it does not start, or it is interrupted the first time texts or characters from this mod in the game). Therefore, the only way to make the mod work normally on BOTH Russian versions of the game (old and EE) is an iconv-transcoder that converts files to UTF-8 if the game is version EE.
In this case, the transcoder was, but it worked incorrectly, because I was a little mistaken when adding the command to start it (HANDLE_CHARSETS). In my previous post, I fixed this. Cirosan, update file in mod, please.