Is it good to put all miners in a box? Does it lower the temperature inside?
No, it would be a terrible idea to put your miners in a box. But if you were to put them in a proper rack enclosure with the right ventilation then they should run at a good temp. and noise may be reduced depending on how it is vented and cooled.
@Mikestang is correct. Simply putting miners in a box is not a good idea at all. But with directed airflow in and out, is drops the over all temp. This restricts hot exhaust from being recirculated.