Questions about 2017 Canyon Ultimate Disc internal cabling

I’ve finally got round to starting my mechnical Ultimate build but I’m a bit confused by the internal cabling. Specifically:

1) Should the cables be used bare internally or with liners (specifically the liners that came with my groupset… not the ones they’ve got pre-installed to help you thread things through)? I was convinced of bare but now I’ve seen Canyon use both when looking on the ‘net.

2) What the hell is this cable tie doing between the down tube bottle mounts? http://imgur.com/kXWuXlu It looks deliberate and important. If I tug on it I can see pulls the pre-installed cable liner with it and if I were to tighten it up it’d pull that liner tight against the downtube… But that kind of implies I should keep the liner as a naked wire here might snag??. Also there’s a black split plug somehow involved in all of this but I’ll be damned if I can work out what that does either.

I’m going to ask Canyon for their advice but I’m interested to hear any real world thoughts and experiences.

Thanks!