What is the difference between 井底之蛙 and 坐井观天?
What you got from Baidu is correct.

井底之蛙: the key word is 蛙. Metaphorically, you can reference a person to a frog, being in the bottom of a well. For example, you can say to someone: 你就是井底之蛙！

坐井观天 describes one's behavior/vision. You can say 不要坐井观天 to exhort someone not to be narrow for his thoughts or vision.