Object Mode and Edit Mode
When adding curves there are some common options like other Objects.
Eventually all the primitive curves will be replaced to use the same curve system used for hair curves. Until this is done, their features will diverge.
They can be converted interchangeably to access the full range of edit and sculpting functionalities.
In Object/Edit Mode, the Add Curve menu, provides a few different curve primitives:
Adds an open 2D Bézier curve with two control points.
Adds a closed, circle-shaped 2D Bézier curve (made of four control points).
Adds an open 2D NURBS curve, with four control points, with Uniform knots.
Adds a closed, circle-shaped 2D NURBS curve (made of eight control points).
Adds a NURBS open 3D curve made of five aligned control points, with Endpoint knots and the Curve Path setting enabled.
Adds an empty high-performance curves object and automatically:
Assigns the active object as the Surface.
Set the surface object as the parent of the new object.
Adds a Geometry Nodes modifier to deform the curves on the surface.
The curves can be edited via sculpting.
Hair curves currently have the following limitations:
No Edit Mode.
Not supported in Wireframe viewport shading.