Tip 1. Use transparent textures instead in ther ordered to have more quality or less polygon 
(this tip is for the people make 3D model)

Tip 2. you able to Use spriters even if the project is 3D in ther ordered to have more options lick animetion and tiling...

Tip 3. you able to have 3D collision inside 2D collision if you make children objects

Tip 4. you able to use animation instead code sometimes

Tip 5. if make cutscenes and you want good quality and work in eny devices event in low specks device's,
one good tip is to use video files.
instead to run in real time,
in this way is lighter and have the same quality to every system,
note if you use this system i have standard resolution and stadard fps is image quality etc.

Tip 6. use grayscale texture if you want to select the colors inside the unity engine

tip 7 if you want code with it working with different controller or you want to have different button various you cen use this examples Example 1 or Example 2