Several questions relating Unity engine

I have several questions i need to get answered before moving to next part of development.

-I am considering using quite a lot underwater plants in game and i am wondering what is performance more costly:
1.A simple 1 polygonal plane with GIF animated plant texture. I dont know how many sequiences of animation would be there but lets say 10 for example.
2.Mesh modeled plant with arround 50 polygons for model and rigged with w bones.
Consider that there should be more than 20 plants on screen at once.

-Wind force faked water movement. Is it possible to add wind force to effect fish and underwater plants for some sort of water movement?

-Using reflection shader (with diffuse, normal and spec maps) on every fish. Up to 20 fish at same time on screen. Would that decrease FPS a lot? I could land on cube map reflection instead proper reflection.

-What is maximum allowed number of rigged models per scene or maybe frame?

the wind one would definately be the easiest, since the terrain already has a tree tool which factors in with. you could just do that and tweak it to look like its underwater