Hi Switchblade,
I’ve covered the shading issue you see between modular pieces here on my Lighting Wiki guide: A new, community-hosted Unreal Engine Wiki - Announcements - Epic Developer Community Forums
This guide includes some tips for getting rid of the issue. Ultimately, for something like your wall you would be better to use a single mesh for the wall or other geometry to cover these seams. Sometimes over-modularizing your scene is not the best option and just increases draw-calls that need to be performed and gives you results like this. Hopefully, we can fix this in the future and this won’t be an issue, but as far as I’m aware there are no plans at the moment.
The wavy shadows are due to low lightmap resolution.
-Tim