The best shape of the gate can be rectangular or close to square, but the gate is the most taboo in Feng Shui. Although there are few triangles, everyone likes an alternative appearance, but it is not good to design the gate as a circular arch just for the sake of aesthetic appearance.
The circular arch is really beautiful and unique, but it can only be seen in temples and Taoist temples, or some tombstones are designed like this. This circular arch belongs to the gate of ghosts and gods, not strangers.