Best level building approach in this case

I have the following room/building setup.

Red lines are basically level cordons (4 big 32 cm thick walls).
One face of each wall is shorter than the other to make 45 degree edge which I then align all 4 by to each other.

My question is:

Should I be removing top and bottom face of these meshes/walls (since they wont be visible to player)?
I heard somewhere that Unreal Engine lets light through invisible faces which in my case will cause undesirable effects like lightbleeding?

Should I also be removing faces on each of the mesh/wall sides (Because they will be next to each other at intersections A in picture)?

Another question I have is about blue lines in my image, those will be walls separating rooms.
My current idea/approach is to make simple plane mesh with texture applied to it and simply place them as walls and scale them as needed.

So I will end up with walls between rooms looking like:


(Blue is visible face that will face room, while black is just back of plane)
So if I stack them next to each other facing outwards - would this work or would I have some sort of lighting issues?

For simple walls I generally use boxes. Deleting the backfaces of walls, which are very simple meshes is, in my eyes, both a waste of time and opening a door for lots of issues harder to solve. Most of the times walls will be completly hidden and hence culled out.

In short, I recomend you to keep walls with all of their sides to be sure lightning will work correctly. If this is for a mobile game and you will use baked lights be sure to enable precomputed visibility to further improve performance.

In current gent games this kind of optimization is deprecated since the difference you will obtaing in performance is almost null (even more if the lights are precomputed).

Another piece of advise is: Do not focus on optimization in the early stages of your game. Get it running, make your level, optimize later if and only if you need to.

Hope it helps. Make it a great day!

The reason I wanted to go with plains is that it makes it easier to build each room different color.

Instead of one mesh having two materials (one side and other) plain can have one material which simply would be set when placing it in room if you know what I mean?

All workflows have advantages and disadvantages. In the case of room walls you should go with the workflow that works best for your purpose. You can always make the materials on said walls as two sided to avoid light leaking from the other side if you decide to use planes instead of boxes.

Thanks, will go with cordones/red walls with all faces on them and try building interior walls as planes, if that doesn’t work as I need it - Will reconsider approach.