What format did you use PS as a banner and finally save it in?

You can save it in any format. If you are satisfied with the drawings you have drawn and there is nothing to modify, you can save them in JPG. If you are afraid that something is not perfect, you'd better save it in PSD, so that when you take it to the printing place to proofread the manuscript again, you can correct the mistakes. Once an error occurs, JPG is difficult to correct.

And if you combine all the layers and save them in PSD format, it is meaningless.

JPG and laminated files, PSD is a layered file, and the content can be changed again.