How far apart will the two boxes (control box and light power box) be?
You could put a microcontroller with sufficient I/O pins (20 plus whatever you need for control input) in the light power box. The MCU would control the lights via the I/O pins, either on, off, or dimmed via PWM. Each pin would need a transistor driver capable of delivering the proper voltage/current to the LEDs or bulbs (what voltage bulbs are you using)?
The control box would contain another microcontroller that reads the controls (buttons/switches/etc.) and sends data to the power box over a cable using a serial protocol like I2C or RS232/485 or whatever.
Not exactly a beginner project.