The Raspberry Pi Pico is both faster and cheaper than the Arduino Nano, but the nano has better resources and community.

Raspberry Pi Pico 2 is faster and backward-compatible, still only $5 The second generation of the popular hobbyist chip just dropped and it has significantly more power than its predecessor.

The PicoCray project connects multiple Raspberry Pi Pico microcontroller modules into a parallel architecture leveraging an I2C bus to communicate between nodes.