Is there any downside of adding IC2 & GregTech later to modpack and to the already existing world? I know i will have to generate new chunks to get all the world generated stuff but are there any bugs or some incompatibilities i should know about?
While ago assembled modpack with 60 mods including IC2 & GT, started the world but after while decided there is nothing interesting in these 2 mods I will ever need. Decided to get rid of these 2 mods and start new world, because with both these mods game loading times are freaking long and memory consumption is massive. Waiting over 5 minutes for game to load and allocating 5GB of memory for it.... 
To be honest GregTech once was fantastic mod, I like complicated and technical stuff, but now it is unnecessarily overwhelming (GregTech 5). So decided to create new world (because deleting both now causes corrupted, bugged world) and start over (goodbye wasted 150+ hours 
) and add IC2 & GT in the end when I have explored and completed all other mods... but not sure if it will be possible later.