According to Nintendo's Tweet: Expansion Pass owners can download it from 14/09, while the standalone retail version will be available 21/09.

So they are delaying the retail version of Torna just so they can put a download code in an empty box? I think not. They would have just shipped a bunch of those little scratch off cards with the download code on it. 

New blade in the DLC, those who played through the story may recognise who this is.

I haven't even tried to do any new Blade quests besides the current seemingly endless grind that is Ursula and her merchant missions. So I have no idea if I am effected or not. Been getting my ass beat in Challenge mode to make Shulk be worthwhile. It is hard.

Played through the first hour of the Torna Expansion, (the part they showed at Treehouse, so nothing new yet) and I was really struck by how much better it looks visually than the base game.

For those who missed it, Monolith have said the expansion uses a new engine that they're building for future games; its still a work in progress so Torna doesn't benefit from its full potential, but they said some improvements should be noticeable, and they sure are.

It just look much cleaner and more vibrant.

Yeah performance is a bit wobbly still, it's mostly just that image quality seems crisper and detail turned up a tad.

https://nintendoeverything.com/takahashi-on-xenoblade-chronicles-2-torna-the-golden-country-new-engine-for-rendering-and-more/

I've been playing Golden Country for a few hours so far, and so far I really enjoy it. It feels different enough from the base game to stand on its own, and adds some cool new features, including one that seems right out of Xenoblade 1. Appearance-wise it looks nice, and the soundtrack is great as usual.

Can't say much of the story yet, but I just got the 3rd driver which seems to be most (maybe all) of the main cast. It's interesting seeing Mythra, Brighid, and even Aegeon interact with their new drivers, and I like the more mature relationship Jin and Lora seem to have. I already cried a few hours in, so it gets going pretty fast!

Probably my favorite part so far is being able to directly control Blades now, both in combat and during exploration. My series of "Mythra standing in front of landscapes" screenshots will only get better!

My impressions might change as I get further in, but so far it seems like a very solid expansion.

Yeah they did say they were in the 'transitional period of refining its use for future games" so Torna won't showcase its full potential, their next game in 2020 or qwhenwever should look far better.

I never felt like the XCX engine was a good fit for Switch; it squeezed incredibly impressive results out of Wii U, but in base XBC2 it was underwhelming.

Not really a matter of fit.  More a matter of not all the additions coming out as good as intended.  Cause technically 2 has a number of features X does not that make it the more demanding game it is.  Godrays, improved lighting, ambient occlusion, a new rendering pipeline, better handling of materials, new folliage solution, improved texture filtering, volumetric cloud simulation, new water shaders, screenspace reflections, higher quality shadows, TAA.  Overall an engine much more in line with current generation standards.  But it seems not all these additions went smoothly.  A lot are welcome but some came out rough.  TAA I hojestly think is the worst result.  The blurring artifacts are very noticeable in a game with a pulled back camera.

So it seems they've gone back and built a new rendering engine to replace this one to address all this.  Bolting new stuff on is faster but never as effective as building a new one in terms of implementing new features.  It's not always practical but I think in this instance it's a good move to prep for the future.