First of all, when PS creates a new file, the default resolution is 72 and the color is RGB. According to your own needs, you can set it yourself when you create a new file. Secondly, do you want to print this cover or do it! If you do exercises, the size is customized, the resolution is 72, and the color RGB is good! If you want to print, the resolution should not be lower than 300, and the color should be CMYK. You can't use RGB, and you can't use RGB first and then convert it into CMYK. But if you print it, I personally suggest that you make it in CDR or AI! After all, PS is only an image processing software, and its text function and typesetting editing are not as good as professional typesetting software! In addition, there will be some cards for resolutions above 300! The printing house may not accept it! LZ, you have to distinguish between PS and CDR and AI! !