If at any time, you are making a “hard” reference to something, so a normal UObject pointer, not a soft one, then it is going to be loaded into memory recursively for anything “hard”. Even if your level manager handles some of this, you always need to be aware of it. Your UI, Datatables, asset properties, textures, sounds, animations etc, all must be soft when possible or a ton goes into memory.
That is awesome 
you might enjoy parts of the ALS (Advanced Locomotion System) which is an animation framework for running , crouching and climbing. It has a free c++ version now on github and comes close to animation seen in Inside. Inside has some very pretty animation responses related to the scene intensity. Right after swimming, falling hard, escaping in Inside you see the effects. Love Limbo and Inside myself.
I think this type of “2D / linear” map is amazing for storytelling. I think one of the best map designs I have seen was actually Dark Souls 1, because you can always see parts of other areas in the distance that look entirely different from where you are. You can totally walk there through a different path and it really feels like a whole. You would be missing that in a true “2D” left to right map but I think that does fit really well with riding the bike. Another type of map design for “left to right” movement which felt surprisingly well you can find in Klonoa 2. It’s linear but some areas are curved and some areas offer vertical exploration and side areas. I see this combine rlly nicely with a Limbo / Inside / Trials combo