dealing with non-visible polygons

I have a character in hipoly, upon which I’m creating its clothes. After extracting the normal maps and low poly meshes, should/could I remove the non-visibile polygons of the lowpoly mesh (eg, the inside of a jacket, of a hat, and so on) without getting any “side-effects”, so to lighteen the burden of the engine, or they are automatically considered as inexistent (mean, the engine doesn’t calculate them 'cause it doesn’t see them) or there’s some option to avoid their calculation/rendering?
Excuse me in the case the question may seem banal or already answered (though I got no idea on what to search).

Yes, you can delete them. Geometry is just that, geometry; there are no dependencies that a model has to be complete or even match a high-poly model it was baked from. To the engine, its just a bunch of 3D points, surface normals and texture mapping coordinates. If you feel a polygon is not needed/visible, delete it.

Note that while the engine would by itself not render hidden surfaces, it still has to detect that they are hidden, which does take some computing resources. So it is good practice to remove anything of which you are sure it is not required.