I spend a lot of time working on fantasy maps, currently I am working on several large shapefiles/geodatabases which in combination cover the whole of northern Africa. I have had a lot of trouble running that much data in ArcProArcGIS Pro, but ArcMap on the other hand, gives me no trouble at all working on such a large dataset. I would suggest working with ArcMap rather than ArcArcGIS Pro if you do not have any need for a 3D viewer.