Fillets the corner formed by two curves with an arc.
Steps:

Select
the first curve near the end.

Select the second curve near the end.
Options
Radius
Changes the fillet radius.
Join
Trim
ExtendArcsBy
Applies when arcs are filleted or chamfered but need to be extended to meet the fillet curve or chamfer line.
Arc
The arc is extended maintaining its validity.
Line
The arc is extended with a line segment, which is joined to the arc converting it to a polycurve.
Curve Tools > Fillet Curves Main2 > Fillet Curves
Curve > Fillet Curves Related topics… 
Fillets the corners of polycurves and polylines with arcs of a single specified radius.
Steps:

Select
polycurves
and press Enter.

Type
the fillet radius.
Curve Tools > Fillet corners
Curve > Fillet Corners Related topics… 
Draws a curve that blends between two curves keeping continuity with the curves.
Steps:

Select
the first curve near the end where you want the blend to start.

Select the second curve near the end where you want the blend to end.
Options
Perpendicular
When Continuity
=Tangent or Curvature, allows you to blend a curve to a surface edge perpendicular to the surface with continuity.
AtAngle
When Continuity
=Tangent or Curvature, orients the direction of the blend curve other than perpendicular to the edge. You will usually need reference geometry to select since you cannot type in an angle value.
In this case, to make a curve to use in the Sweep2
command with vertical ends but not be a trimmed surface, snap the angle to the upper endpoints of the vertical reference lines.
Hold the Shift
key, to restrict the angle direction by ortho but keeping it tangent to the edge curve.
In the video, the red curves are blended at the angle determined by the vertical blue construction lines.
Curve Tools > Blend Curves
Curve > Blend Curves Related topics… 
Creates a blend curve between curves and/or surface edges with control over the blend continuity.
Steps:

Select
the curves.

Select a control point to adjust.

Press the Shift
key and select for symmetry.
A preview of the curves displays that allows adjustment of the curve before it is made.
Selection options
Edges
Restricts selection to surface edges.
Point
Specifies a point to blend to.
Curve options
Shift
The Shift
key controls symmetry. By default the shape curves are separately edited at each end, with symmetry, point editing is mirrored to the other end of the curve.
Flip
Trim
Join
Display Curvature
Displays the curvature graph
.
Continuity_1/Continuity_2
Surface Edge Options
Keys for control
Alt
By default the shape curves are perpendicular to the surface edge. Hold the Alt
key while dragging the handles to change the angle between the shape curve and the surface edge.
Shift
The Shift
key controls symmetry. By default the shape curves are separately edited at each end, with symmetry, point editing is mirrored to the other end of the curve.
AtAngle_1 and AtAngle_2
When Continuity
=G1 or greater, allows you to orient the direction of the blend curve other than perpendicular to the edge.
Curve Tools > Adjustable curve blend
None Related topics… 
Places a line segment as a beveled corner between two curves.
Steps:

Select
the first curve near the end for the chamfer.

Select the second curve near the end for the chamfer.
Options
Distances
The distance from the intersection of the curves to the chamfer.
Join
Trim
ExtendArcsBy
Applies when arcs are filleted or chamfered but need to be extended to meet the fillet curve or chamfer line.
Arc
The arc is extended maintaining its validity.
Line
The arc is extended with a line segment, which is joined to the arc converting it to a polycurve.
Curve Tools > Chamfer Curves
Curve > Chamfer Curves Related topics… 