Questions about landscape tiling & world machine

Hello everyone, I finally managed to get my hands on World Machine, and after making an awesome island, I found a tutorial on the UE4 wiki (A new, community-hosted Unreal Engine Wiki - Announcements - Unreal Engine Forums) and followed it, one of the steps in the tutorial was to tick the box ‘Flip Y-Axis Orientation’. After doing all of the steps and building my tiled landscape, upon importing it to UE4, the landscape was of course flipped on it’s Y-axis, which I do not like one bit. So now I have a few questions:

•Is it necessary to flip the Y-axis? (I would just untick the box and try again, but I don’t want my PC to be slow for the next 3 hours)
•Once I import my tiled landscape into UE4, how do I position/rotate/scale my tiled landscape?
•Does my tiled landscape automatically level stream based on current game performance? Do I need to manually adjust settings for level-streaming?
•What are wheightmaps?
•In the UE4 docs, I read about using LODs with Simplygon, but I cannot seem to find where to manually import other LODs of my tiled landscape, how do I do this? (I would use Simplygon, but each tile exceeds the 1 million polygon limit for free Cloud service)

Thanks ahead of time, I am looking forward to hearing your answers.