Hi Michael,
The short answers to both questions is yes. Beziers are different to circular arcs, and they are a supported geometry type for features in a parcel fabric. There are, however, some limits to using beziers in the current release, described below.
Additional information:
Feature geometry is built up from segments. A segment can be a straight line, or a parametric geometry. A parametric geometry can be a circular arc, an elliptic arc, or a bezier. These parametric geometries are referred to generically as "curves", but when used in the context of parcel data and COGO we are, 99.9% of the time, referring to circular arcs. In the COGO world "true curves" and circular arcs have become synonymous.
Limits of beziers when using Build command:
Beziers may be used in the fabric model to represent natural boundary features, however we have seen cases where straight lines have been turned into bezier curves even though they are still geometrically straight. Beziers should be reserved for natural boundaries. If your fabric has very large natural boundary features with many bezier curve segments there are known limits that cause performance problems when running the Build command, for example. These issues are being addressed and fixed for the next release of Pro. (3.1) We are also investigating the feasibility of providing a patch for this on earlier releases.
What about transition curves and spirals?
The other curve we see in COGO workflows is the "transition curve" used for highway and rail centerlines. This incorporates the use of spirals, and combining them with circular arcs and/or straight lines to form smooth, tangential transitions to represent long linear features. Spirals cannot be represented parametrically in Pro; they are handled differently and are represented as a densified polylines. (For more specific info see this topic in the Concepts documentation for the COGO SDK)
-Tim