I'd say that Hatsune Miku no Shoushitsu is quite popular, so if you haven't heard it yet, you could listen to that one.
(Yanhe) Execution by Lian Shang
(Dex) Honey I'm Home by GHOST
(Miku) Sekai no Subete by wowaka
(flower) Neru by annyahoo
(Miku and Gumi) Kitsune no Yomeiri by masa
(Len) Dappou rock by Neru
(Rin) Jailbreak by Neru
(Yuezheng Ling) 俗 by Lian Shang
(Oliver) The Problematic Crow's Reality by pghostyboo
From what I have seen, Miku is a contralto that is capable of hitting soprano notes. Her voice range is up to E5 based on a quick google search. Although different sources are saying different things. Some say she's a contralto and others say she's just an alto. I wouldn't be able to actually test it, as I do not own her.
The vocaloid with the highest range I could find is SeeU, a billingual voice capable of singing in Japanese and Korean. She can sing up to C6, which is pretty high.
The lowest vocaloid I found is Big Al. He can sing down to G1, and he's the only one in the bass category on vocalopedia.
Okay, I admit I didn't look around very much, so there might be vocaloids with higher or lower ranges than these, but this might be helpful.