What is the best method to pipe in order to get a smooth transitions in both directions?

[diff-arch]

MultiPipe in Rhino 7!

Check this out:

Now, if you don’t have Rhino 7, you can use @DanielPiker’s Fattener (link) component add-on for Grasshopper to get a similar result. This will give you a mesh, whereas MultiPipe produces a SubD.