That post was a bit confusing. The point that (I think) they were trying to make is that in bag style slings, it's basically impossible to position a newborn so that they can't curl into the "C" position. However, none of the carriers you mention are technically bag style slings.
The Nojo and the OTSBH are what is called a "closed tail" ring sling. The Maya Wrap is an "open tail" ring sling. A closed tail sling makes it much harder to position a newborn in the safest position, upright and facing the wearer, because it doesn't allow for a piece by piece adjustment around the baby. The Maya Wrap with it's open tail does allow for this, and does the job pretty well too. The Kangaroo Korner, as an adjustable pouch, is usually used for a cradle type carry with a newborn. I found though (had a fleece KK) that the extra depth of the pouch actually made for a fairly decent, legs in front carry for a newborn. You just need to make sure it's snug enough. Your mileage may vary there, though.
So what should you be using with your new baby? Well, simply put, whatever works best for you.
There are a lot of very safe options for newborns. My top two recommendations for the newborn period are (open tail) ring slings and wraps. Both will allow for fine tuning the tightness of the carrier around the baby and give proper head, neck, and back support. The runner up to those would be a mei tai. As a fellow plus size mama (somewhere around a US size 18) I can say that I have worn all different types of carriers and never had a really hard time finding one that fit right. From an aesthetic point of view, ring slings and wraps don't accentuate the "fluff" quite so much as mei tais and buckle carriers, which tend to have thinner straps. Wraps come in a variety of sizes, ring slings can be made longer, mei tais come with extra long straps, and even some buckle carriers are made with plus sized wearers in mind.
So do some online window shopping, see if there is a babywearing group near you, and just dive in. I'm sure you'll find something that will work.