Arduino UNO uses ATMEGA328P-PU microcontroller and this controller comes pre-loaded with a Arduino UNO bootloader. Basically bootloader is a little piece of code that allows you to program the flash memory of the Arduino’s atmega328p via serial or USB instead of using an ICSP programmer.
Arduino Nano Board R3 CH340 chip With USB Mini Cable (soldered) The Arduino Nano Board R3 CH340 chip With USB Mini Cable chipboard is based on famous Arduino platform and does all the functions of Arduino Uno, but with a smaller footprint.
BRAND - Geekcreit® ATmega328P Arduino Compatible Nano V3 Module Improved Version With USB Cable
The board has one relay which works on 12V but the input signal can come directly from microcontroller output working at 3V or 5V to control relays.