I was just looking over old conversations and arguments about the "superiority" of canard emplacements, but...
I think I proposed a while back the concept of a J-20 as a developmental platform, a sort of anti-F-35, in that it can be progressively upgraded to newer and better capabilities. One of the key points was that if the J-20 had reliable TVC, it could eschew tailfins to enhance maneuverability.
When I was called out on this, I was unable to come up with an adequate retort, but if you look at the documentation around the American X-36, this can be easily explained.
Tailfins provide stability and yaw control for most aircraft, and V-tails provide a combination of roll and yaw. With present aircraft, they are a necessary feature, enabling maneuverability and stability. With the X-36, split ailerons, like the ones used on B-2s, combined with canards and thrust vectoring, were used to provide an alternative source of yaw control. This allowed the experimentalists to remove the tailfin on the X-36, further reducing its RCS and drag.
With regards to the J-20, I suspect that the J-20 will come in three phases.
The first would be the J-20A, with initial operating capability, decent stealth, speed, range, and adequate maneuverability. It would be able to have a combat range of over 2,000 KM, as well as be able to knock out enemy fighters in BVR and perhaps be able to snipe out AWACs aircraft from long range and high speed, although it appears it lacks the weapons bay for this purpose (you really want ~300nm range AWACs killer payloads on the J-20! E-2Ds will be able to reliably detect the J-20 using its VHF radar at maybe 200-300 nm, so better reward them for their snooping by killing them while out of range of their fighter escorts!)
The second would be the J-20B, which would probably have enhanced engines on top of the J-20A, perhaps with enhanced thrust to weight ratios and perhaps first-generation thrust vectoring. This aircraft would probably be able to outmaneuver the F-22, given that it's a newer aircraft, it uses a novel aerodynamic layout (lerx-canard-lerx-delta-lifting body), and has TVC as well. Against the PAK-FA, it may be mildy inferior, or it may be around the same WVR capability, or even better. It doesn't matter that much, though, since the PAK-FA is not that optimized for stealth and if the J-20 wants to pick a fight (against perhaps the Vietnamese), it would probably be able to kill it in BVR.
The third version would be the J-20C, a tailfin-less J-20B that relies on TVC to ditch the tailfins. Perhaps the delta wing would be modified as well, as the tailfins and strakes are necessary components of its infrared emissions control scheme and different engine exhausts would be necessary for this feature, adding perhaps split ailerons as well to increase stealth and compensate for the loss of yaw control from losing the tailfins.
This version would have moderately reduced drag compared to the A and B versions; the X-36 is supposed to have 10-20% less drag than the F-15, while the already small tailfins on the J-20 would likely reduce the drag reduction to 10% at best. More importantly, the removal of these tailfins would reduce weight, as well as reducing RCS; resulting in both better maneuverability and better RCS reduction compared to the A and B versions.
