In my game I am facing a performance dilema. There are 2 ways of optimising that I will use. And I need to know how many triangles are actually rendered in game per frame to find and make balance between them to render as least triangles aspossible at one time
There is no one answer to this questions. The types of shaders applied to surfaces and the number of separate objects has a big impart on the performance of the system.
For example, you could have a model that is just 1 triangle. If you duplicate this model 10,000 times Blender will probably have difficulty rending it. But Blender can handle a single model with 10,000 triangles pretty easily.