Is it fixed how fast i can switch scenes?Can i switch scenes faster with python?
It’s primarily dependent on the amount of meshes you need to load. Using Python will take the exact amount of time unless you switch to an empty scene and then load the objects dinamically (wich will take longer to load completly but switchig will be super fast). It is worth it? Probably not.
What is the difference in using libload,libfree or add object actuator.Which takes more resources and lowers the framerate more?
Libload and libfree are part of the same API, with them you can load things from other blends once the game is already running instead of loading all at once at the start of the game. Here I mean load to the RAM, not to the GPU. Once on the RAM they move to the GPU if the mehses you load are visible etc…
The add object actuator and the addObject API (from Python), load something of the same blend file (already on the RAM) to the GPU. It is faster but your game will conusme much more RAM all the time this way (of course if the game in not so big it may just be OK to use this method)
Finally switching a scene consumes some time for the switching itself but most of the time consumption comes from loading all the objects in the scene to the GPU at once, you can do it progressively by using any of the avobe methods (wich will make the switching instaintly but will take time for all objects to be loaded on the scene). Depending on the game you’re making it is just not worth the effort, so think carefuly if you really need this.
Of course once everything is loaded the framerate will be the seem for them all.