I will guess SCARM is some sort of design/building block design tool tailored to model railroading, but it's not terribly important unless it confines you to designs with fixed angles (like sectional track does), in which case it is of limited usefulness, IMO.
You have the same design problem here in all five cases, and it's one to be avoided regardless of chosen radius, and regardless of whether the track is hidden or not: Do not directly join curves turning in one direction to curves turning in the opposite direction.
[You have those faulty joints horizontally to the left of all five of your radius descriptions]
ALWAYS have a section of straight (aka "tangent") track between the two. Recommended (but not ideal) practice is to use a section of tangent equal to or longer than the length of the longest equipment you intend to run. In most cases that will be something like 85' passenger cars, or 89' flat cars, which is about 6 3/4" in N scale. If you don't do this, you are just begging for problems with "coupler swing" or "coupler gathering," and you can look forward to many, many derailments at or near those spots.
Something shaped more like a rounded ice cream cone (triangular) and less like a drop of water is what you want.
