Don't render objects behind other objects, or use transparency flags? (Like Source engine)

Questions & Answers
1

My game has barely any transparent textures, and I need good performance because I build on Android.

Is there any way to give objects flags that define wether objects behind them should be rendered or not?

The Source Engine works that way. I was playing with the console and found commands to hide all non-transparent objects. When I did this, most props like barrels or crates disappeared.
Can I somehow do that in Unity?

EDIT: Does the “cutout” render mode work this way?

2

What you need is Occlusion Culling.