KDE doesn't require the user to use double click unless he sets this as his kde wide setting, I think Juk should try to follow that rule too.

In Juk when I want to jump to a certain song I can't do that any other way then to double click on the song in the playlist (or maybe press next or prev many times ;)

I suggest to change the behavior that when the user plays song A, clicks on the playlist on song G that pressing 'play' will start playing this selected entry.
To keep things consistent I'd also suggest to make juk behave accordingly when switching songs. In the usecase above, if the user doesn't click 'play' but instead waits till the song ends the song that will start playing is song 'G'.

Background here is that I want to use Juk on a touch screen machine without keyboard or mouse.  Its very hard to do so right now as both right click and double click require quite some dexterity.