120 segments for an arc is way, way too many for nearly any imaginable purpose, certainly for a surface whose only job is just to sit there and be looked at. There are many adverse consequences to using more segments on curves, arcs, and circles but hardly any upside.
First, do not judge the the smoothness of an object’s appearance if the object is just a 2D outline. Once the curve is incorporated into a shape, and the shape extruded, you will see that number of segments doesn’t play nearly as great a part in apparent overall smoothness as other factors, including uniformity of mesh size. When you look at a 3D object whose curved surfaces have been softened/smoothed, it’s really hard to discern individual facets and very hard to tell the difference between a surface consisting of a hundred facets or five hundred. Or a thousand. The only time the number of segments really makes a difference is when you are looking at a curve in profile, as at the end of a cylinder.
You must reset your expectations as to what constitutes a suitably smooth curve. Seeing segmentation sometimes in somes views is inevitable. Get used to the idea.
The alternative is a big, massive, unwieldy model that gobbles up system resources, makes your computer move at a crawl, and is subject to mysterious failures, especially on intersections.
When you use Follow Me to extrude a curved profile along a curved path, the number of facets on the resulting surfaces increases exponentially as you increase number of segments on 2D curves. The resulting surface is made up of thousands of teeny, tiny faces. The more faces make up a surface, the smaller they are. The smaller a face is, the more likely is is to fail to form. Faces with any dimension less than about 1mm simply do not form, and cause holes and voids in the surface, or torn, uneven-looking intersections. Sound familiar?
Make better models: try using the default number of segments on curves. Constantly look for opportunities to reduce the number of segments. Never increase them without a specific, compelling reason. Do not judge the appearance of a model, especially its “smoothness,” based on 2D shapes.