sPlKe very good explanation, looks like you have good experience
I also will try give useful info.

Do not use sprites for grass(there lot of grass), use single model. In some cases this trick do not work.

Models(mesh) rendered faster if has less number subsets (parts of the mesh with different skins).

Reset DYNAMIC flag for static models.

Configure some ODE(physics) value for good framerate. ph_fps_max_lock,ph_check_distance,ph_iterations

Set preload_mode to 3 if you do not want sudden 'jerks'. (In slow PC)

In manual not much info about rendering of level geometry, so I want to share my observations.
A7 commercial version render main level geometry without using portals so all level geometry that hidden behind the wall also will be drawn , so with this features you can not do big indoor level or use complicate pixel shader because you will get overdraw