"On good form" doesn't exist. "In good shape" can refer to a person (often literally, referring to their weight and strength), but it can also refer to abstract things. In that case, it means the same thing as "on track" or "coming along nicely" (making good progress). Example: "Our team's project is in good shape. We will definitely finish before the deadline."

First, note that quotation marks go "up top", not ,,down below,,. But to answer your question, a person can be "in good shape" or "in good form" or "on good form. "In good shape" usually means that they are healthy, but also physically fit and strong. "in good form" usually means they are healthy and cheerful, or that they are performing well at their activities. ("In good form" is not used very much in American English). Examples: I've been going to the gym a lot so I'm getting in good shape." I saw Tom yesterday. He seems to be in good form again after getting COVID last month."