Hey there, what is the style of the rest of your kitchen?

I assume you are looking at Miele 626x series oven. The Culinario H6267BP is a very good choice. There is a promo 600$ off at the moment till November 30th, see http://www.miele.com.au/domestic/cooking-baking-8-3219.htm. The flexiclip that comes with the oven is very handy and can be left in there in the self cleaning cycle. The perforated tray is also great for bread baking. H6267B is still a good choice, if you don't want to pay for pyro function. If you are set on Sirius brand, SL906 L850 is another option. Baffle filter works pretty good; I have one on my big whispair undermount unit. The perimeter extraction in SL907 may work fine. It will depend on your cooking. SL906 probably can extract air better, but it does not look as cool.

Yes, but are you using the gap where rangehood was to centre, or the centre of the cook top. If you have cabinetry along the wall then you can hide the fact that the extractor fan/rangehood is not centre of the cook top. Or that is how it appears in your photos.

For the small amount of range hood that would be in contact with the undulating subway tiles, I do not see a problem.