Any Raspberry Pi will do you. A Pi Zero is very small but this doesn't limit it's functionality. The latest is the Pi 4. Model A and B versions can be picked up cheap on eBay.
Main consideration is a good power supply. A standard phone charger fits all except the new pi 4, that's USB C, but you need at least 2amps output.
I run my Pi's "headless" That is I set them up initially connected to a keyboard mouse and screen with a wifi dongle - set a static ip address - then use SSH and VNC viewer to connect to the PI from my PC.