LOD hack not just controls objects LOD level, but increases objects visible distance (most objects has their own maximum distance value, at which they became invisible). what is "cvar", polygons number in the scene? if so, lags appearance was caused by something else, LOD hack still increasing number of polygons and nothing more.
EO LOD level is exactly the same, just for rendering EO picture - FLIR image for example will be more detailed at high level.
you can see what mods was included in main version at this page -
http://eechcentral.simhq.com/index.php?title=EECH_developments_and_timelineMi-26 was never made. and it will not replace Mi-6 - I am personally against about removing any available helicopters, but it can appear in the future as additional aircraft.
old DDS textures doesn't work (some mods for EECH versions earlier than 1.16 can contain them).
I am not responsible for sound changes, but as I know DS version was deprecated and not available anymore.