The Arduino Nano itself is the most basic and oldest of the group, and just like its many iterations, it's designed to work primarily with breadboards, making it a great tool for prototyping.

While the pinout is very similar to the Arduino Nano’s, there are four (12-bit) analogue inputs rather than eight (10-bit). Some digital GPIO pins are numbered differently too.

An Arduino Nano or a Micro might be the best options If a small board sounds like the most appropriate choice.