Try to take an HighScreenshot from top to the Scene-Depth buffer. And export to WorlMachine or photoshop > blend layer > Lighter color (this will maintain the brightest values of white…the displace). Combine them.
Then reimport to Unreal engine, and reduce down the value of the displace to compensate. Not perfect but helps.
I use this for DX11 tessellation (I dont use offset)
To compensate the walkable zones:
haven’t tried it myself but they added a feature just for this purpose.
select your landscape and in the Details Panel look for “Bake Material Position Offset Into Collision”
glad you found a fix for the issue, but adding a bigger bounds would [on the paper] just cause more rendering overhead (some components will be rendered even if they are out of the view) though it might be negligible due to the fact that it’s only a Z bounds extension.
I’m curious if this other method would fix the original issue: go to the landscape tools, find the one called “Change Component Size” and just hit Apply. this will in theory re-create the landscape so the collision should get a fix if anything is wrong
using “Bake Material Position Offset Into Collision” might just fix the original issue too
I am working on a new landscape for my pack now and didn’t have the z fighting issue on it when adjusting the WPO. Also the bake into collision worked perfectly well. Thank you. 
