In my opinion the Giulia's five-hole wheels look better than the 4C's. Putting my helmet and body armor on now.
Interestingly if you check, 18" wheels that are styled almost identically to the Giulia 5 holes are available for Giulietta. I am not sure if the offsets are the same, but the bolt pattern is the same. However, Giulietta has 12mm lug bolts while Giulia has 14mm lug bolts; it is not clear if they can be adapted for use. I don't have any info on weight ratings either.
The 4C wheels look like 5 horseshoes to me. Although both 4 leaf clovers and horseshoes are symbols of luck, I don't think there is any history of using a horseshoe symbol at Alfa Romeo.
IMO the 19" Giulia 5 hole wheels are amongst the best looking wheels on the market. It is too bad that there is no light weight version.