3 options you can duplicate an arcgis pro project
option 1. Dupliate the map frame only, this is best, because you can switch between your new map and original map easily. You don't have to open 2 ArcPro. any update, any change on your origianl map will automatically reflected in your new map. You don't have to update twice by open 2 ArcPro. Because you new map and original map lives in single ArcPro folder, lives in single ArcPro project file, therefore they share the same resources.
option 2. Save As original as single different ArcPro project file (not the whole arcpro project folder). They does share the same resouce but you have to open 2 Arcpro by 2 separated arcPro project file.
Option 3. simply copy whole arcpro folder to another location. most people already know this, I would not show it here.