Shaders & Shadows: How far can I use for my mobile game for good performance?

Hi,

My game is kind of a match-3 game on a rubix cube. It has 9x9x3(243) color cubes to be matches where 81 will be visible at a time.

I am fascinated by the physical based shaders available in Unity 5. But I can clearly see the frame rate reduces according to the shader I use even in my laptop. When I use the transparent shader it drops below 30. Coding-wise I am so conscious about the algorithm I use to have nearly no loading time.

1. Is having 243 elements with rigid body and colliders in the scene too much to carry for a low end android phones?

2. what is optimal framerate for a mobile game? How to achieve a uniform framerate?

3. And everything that you want to advise regarding the question.

Thanks, Karthick.