Used it for Minecraft server for a week then never used it again. Don't know anything it would be good for that my computer can't already do better tbh
Modern amd64 CPUs will run circles around it. Pickup something with a i5-6500 and you will have a much better experience. You also could go older or newer depending on what you are doing.
Likely cheaper and the power usage will depend on the hardware. In idle it shouldn't pull much power. The raspberry pi has gotten a lot more power hungry while also being poor on performance and overpriced.