What I know hmm
Snakes in the anime originate from the Ryuuchi Cave, it is also there that someone can learn Snake Sage Mode (A goal of mine). Some of the main users in the NV of the snake contract are Orochimaru, Kabuto and Sasuke. Each of these 3 had a special boss summon for themselves, Orochimaru with MAnda, Kabuto with Manda 2, and Sasuke with Ando. Snakes have been seen varying in a different amount of sizes but just because a snake is small does not mean it is inefficient it will always have a use. Both MAnda and Ando had the ability to talk like a regular human where the other known ones were not seen capable of this.