what's difference between synchronous and asynchronous and callback for grpc cpp server?

I have read tutorial and googled for this question, but still have some confuse. here is my understand about their difference, but I'm not sure whether it's right.

1. callback is also an synchronous style
2. synchronous and callback grpc cpp itself manage request and response queue and thread model, but asynchronous let user provide a thread management, am I right?
3. sync and callback sytle is not multiple threaded, am I right?
4. synchronous and callback have same performance, but asynchronous style can archive very high performance?