1. As long as you won't run Chunky after you add DH, everything should be fine
2. It should only generate LODs, if you wan to make sure it does that, you can always change the mod to PRE-EXISTING ONLY
3. The best practice would be to not use Chunky at all and use DH pre-generator on a mode you want, but you already used Chunky, the LOD pre-generation is up to you, LODs will take up space, but won't cause any generation lag, though LOD generation is very quick and isn't a heavy load. I would say leave it as it is