Luggage advice

I used to fit a lightweight Tubus Fly rear rack to my Ultimate AL using a Salsa seat clamp with fixing lugs for a rack, and a Tubus stainles J-bend bracket. You need an MTB skewer, but it worked well. However, my Ultimate AL eventually cracked at the brake cable port in the top tube. Maybe that was because of the rack?

as an owner of apidura saddle bag. I'd go for caradice sqr. cheaper more waterproof and easier to put on and off the bike than apidura. Also don't wag like a puppies tail.

Loving the Apidura bags. They have a new waterproof range too, which may be worth the extra $$ if you're doing the NC500. Alpkit also really nice. You're looking at a solid £300 to £500 for a complete setup though, which you will, if you're going for 7 days. 

The days of the touring bike are numbered I reckon. Guys were doing the Indipac race (5500kms) with carbon race bikes there. Saw Tarmacs, Supersix's, Cervelo S3's, Ultimate SLX's.. all sorts. The trendy Curve Ti frames that were on show were really just for bling factor. Titanium repair is harder and rarer than carbon fibre repair I hear. That said, would love a Ti bike for touring, something about metal makes you think it's tougher than carbon. Anyway, with the new bikepacking lightweight kit that's out, you just don't need a full on touring bike. Everything just straps on. 

I've been most impressed with the design of Apidura bags. See the pic on this page of the frame bag, and saddle bag.

https://www.apidura.com/shop/

Though, I'm not sure why you're so reluctant to use your tourer. Isn't that the point of the tourer - to be more comfortable over longer distances?

Have you actually planned what you need to take with you yet?

my advice is use the audax bike and forget about loading up the lightweight alu based frame because you're making hard work for yourself. I don't understand what aspect of using the audax/tourer is going to destroy your body and soul, is it just that it's a few pounds heavier?

of course it is doable but it'll cost you plenty, it won't be as sturdy a fit as a bike designed to accept racks/guards directly to the frame.

You can fit a pannier rack without the need for eyelets on both the rear and front, frame bags can be useful though can hit your legs on them, bar bags are okay but don't load them with too much kit unless you're used to having the handling affected with the extra weight.