Blender Meta objects are implicit surfaces, meaning that they are not explicitly defined by vertices (as meshes are) or control points (as surfaces are): they exist procedurally. Meta objects are literally mathematical formulas that are calculated on-the-fly by Blender.
Sharp flag is used by the split normals and the Edge Split modifier, which are part of the smoothing/customized shading... Crease...value between (0.0 to 1.0), is used by the Subdivision Surface Modifier to control the sharpness... Edge Slide...selection must define a valid loop
Grid Fill... best predictable result can be achieved if you select two opposite edge loops with an equal number of vertices. When a single, closed edge loop is selected, the Span/Offset options allows you to adjust the way two opposite edge loops are detected
The Bsurfaces addon, build in Blender 2.8, creates mesh from annotation strokes... Meaning that you can use the Bsurfaces addon create meshes or use it for retopology.
using the curve
In order for sculpting to give accurate and predictable results, Blender needs geometry to work with. One way to accomplish this is starting off with a highly subdivided mesh. The other way involves using either of two adaptive sculpting methods to add geometry dynamically... The Multiresolution Modifier can be used to dynamically subdivide the mesh.