So basically... I'm led to the conclusion that...

Nega-Tails = Amy
Anti-Tails = Jet

Both are immensely similar to Sonic at their core, but lacking in very specific traits that separate him from them. And as a result, both are practically opposite to Tails in different ways, who himself is a reversal of Sonic's traits whilst also trying to imitate and follow him.

Tails, Amy and Jet all follow/chase/race Sonic. Tails trying to keep up up with Sonic and imitate him, Amy trying to catch up and win his heart, Jet trying to outpace Sonic and assert his superiority. And thus, all three have some variation of matching Sonic's speed.
Tails through flying in the sky.
Amy through her intuition/fortune telling/Sonic Radar.
Jet through riding the wind as its master.

Which must be why I think of Tails as Sora, Amy as Kairi and Jet as Riku.