No probs!
In terms of the foliage models you can select their mesh asset, right click and replace with a lower detail version, if their from megascans it's a case of downloading the lower detail one and doing a switch in the ue editor.
The maps were done just right, it's just the inner 'corridor' level had some parts to the side where it was possible to run off and between the player part of the level and the middle distance mountains. So yeah you could 'get out' as the player!
These arent even things that are even 'wrong' its just part of the process of working through and tweaking it.
We'll have to set up a group of some sort, but in the mean time feel free to post on here with any questions and updates!