Honestly, not gonna front, Marowak and Meowth are both pretty passive design changes. This is something I feared, these Alola forms would only go to Gen1 'mon in an effort to make them more relevant and possibly reel in nostalgics while putting little amount of effort into many differences for these forms. It almost seems like something that could be done to possibly appeal to GO fans in a sense. Unfortunately these Alola forms clearly mean the Gen1 dickriding ain't ending any seen and I had enough fanservice / gen-shilling to last a lifetime in Gen6. I really wanted Alola to most stand on its own feet and not piggyback off past regions and their Pokemon to mainly generate hype and activity.
On the other side of the coin, despite Alola Meowth being just a color swap of Meowth, I do like the lore attached to it about it being the color it is due to royalty on Alola breeding them that way. Literally reminds me of Purrloin, cat, walks on hind legs, troublemaker, purple.
I don't see passive changes, I see clever ones.
Alolan Meowth is a reference to the American Russian Blue. You see, after World War II, the Russian Blue (a breed of bluish gray cats) was brought stateside. However, its numbers were limited, so the modern Russian Blue was bred via cross-breeding with none other than the Siamese cat, which serves as the basis for Meowth and Persian alongside the maneki neko. All that being said, the Russian Blue is still a somewhat rare breed, which could explain why the Alola Royal Family value their particular breed of Meowth.
As for Alolan Marowak, I enjoy the thin, almost zombie-like design. As far as I can tell, it is based of the Hawaiian myth of the "Nightmarchers". The Nightmarchers are the spirits of departed warriors, that appear bearing torches during the nights of Kane, Ku, Lono, Akua, or Kaloa (those are different phases of the Hawaiian lunar calendar). They are also said to appear before their relatives, even during the day, when it is time to guide them into the afterlife, which connects back to Marowak's connection to Cubone.
All in all, I like the direction they took. They may seem subtle, but clearly a lot of thought went into these new designs. I say kudos to Game Freak on this one!
But Cobras don't detach their tails. Their defense against mongoose is venom and their size.
Cobras aren't colubrids so they don't strangle prey or predators.
Cobras rely solely on their venom.
If Arbok had to adapt it would either get camo that keeps it hidden or bigger fangs or stronger venom to be able to take down predators.
I know cobras aren't colubrids, but I did take design elements from certain colubrids when designing its patterning. Besides, I was also drawing influence from Koga's Arbok in Pokemon Adventures, whose special pattern allowed it to regenerate, and who could control its detached tail, as well as Agatha's Arbok who had access to a pattern that granted improved Speed (which I used in my Alolan Arbok's design). I put a lot of different influences into my design to try and make something interesting, but you are entitled to your opinion