It actually doesn't matter if you map in Soft or Normal, both are rankable. Just don't use Drum Samples because the current default Taiko Hitsounds have no Drum Samples. The feature itself is practically not needed because Clap and Whistle has a really small difference which you won't notice unless you use both and listening very carefully.
I map with the Taiko skin - which takes 5 seconds in total to leave Edit Mode, change the skin and go back. I am not sure if you have such time issues.
Instead, you can support the idea for a Taiko Edit Mode with Kat, Don, Big Don/Kat, Drum slider and Spinner as hitobject elements. That'd work better than enforcing every whistle to clap.