Generally speaking, neither of these houses produce traditional Arabian perfumes. At least that's the way I perceive them.
While Montale uses many of the same ingredients used in traditional Arabian perfumery, the overall effect seems different to me. In comparison with Arabian perfumes, I find Montales to be thinner, leaner, lighter fragrances than the typically fuller, rounder, heavier, far more resinous fragrances produced by firms such as Qurashi, Ajmal, Yas, and Arabian Oud. To my nose the oud used by Montale doesn't smell much like the oud used in the traditional oil perfumes. I have sampled a number of Montales, and own several of them. They are well made fragrances. I like them, but I much prefer the scents made by the other houses mentioned above. Other Basenoters will have different opinions.
I prefer Amouage to Montale overall, but until some of their recent offerings such as Homage, Lyric, and Epic, their products haven't had much to to do with traditional Arabian perfumery. I love Gold, Sliver, Dia, Jubilation, Ciel, and even the much maligned Arcus, but these seem more European in style than Arabian.
I'm not familiar with Greyland, but if it's the same quality as Dia and Jubilation, you've got some fine scents headed your way! Enjoy them for what they are, but don't confuse them with the traditional Arabian smell. You can get an idea from several of the ones in the Montale Aoud line or you can check out some of the more recent offerings from Amouage that are more traditional in construction. But for more authentic traditional perfumes, look to the Arabian houses listed above.