Is subsurf the only way to get smooth curvings?

Im trying to make a letter in 3D, building it from scratch

I started with a vertex, and traced the shape I want. Then I fill it with quads and give it an inset. I know I can make the curves of the letters nice and smooth with Subsurf, but is this the only option to get smooth curves in this project? When I use autosmooth for example…the sides look alright…but the you can still see the straight lines between the vertices.

I know I can add more vertices to make this more smooth, but without the subsurf I will still see the straight lines between the vertices…

Or is there a way to bend the edges between the vertices?

Im just looking for a way to bypass the subsurf, to get a nice smooth letter shape with decent topology.