Short answer I just don'r have time to make LOD's and bake high poly detail onto low polys. I am aware of the processes to optimize for a game but I'm just making this as a chance to practice substance painter and get to know UE4 a bit better.
I'm playing it too, I'm at the part with the two key cards. The proportions are easy to scale in UE4 I'm just getting crap in there to have a look at it. I spent my whole evening working on a door just to scrap the texture I can't get it to look like I want it to, very unproductive day. Weekend should get a bit done.