One of the many great things about this series is that they went with a muppet rather than doing him in CGI. I've always felt that Frank Oz's physical Yoda was far more expressive than the voiced-over CGI version of the prequels.
Baby Yoda Grogu has held to that, showing all kinds of expressiveness in his scenes. I don't know who the puppeteer is, but he (she?) does a great job with him.