I find funny every time people question about j-20 by its size...F-22 and Su-57 are both competent dogfighters probably in many flight envelopes but dogfights generally almost always trend towards lower speed and altitude as time progresses. So supersonic dogfighting isn't really a thing (depends how you define it) but supersonic agility to position yourself is key to winning dogfights if it's guns only. There's plenty of indication that the J-20 is quite a capable dogfighter, perhaps only let down by its size if anything. Watching its turns in the most recent showing where the PLAAF really still held back, is enough to know. Long arm canards, high thrust to weight with WS-15 (assuming net mass around 18 tonnes), extremely high lift generation, and low drag, no known aerodynamic shortfalls = at least a decent dogfighter. Anyway it's all on the pilot when it comes to WVR.
The short range missiles on 5th gens are really a last ditch in case they somehow get into a dogfight. They're also mildly capable of shooting down air to air missiles apparently. At least approaching that level. PL-10 also has pretty long range for a SRAAM. Sneaking up on targets as a stealth fighter is possible. There's a lot of cloud covering visual ID chances so it's not exactly out of place at all for 5th gens to carry at least 2 SRAAMs.
Let’s see, f-15 is 19.5 m? F-22 is what 18.9m ? and oh flanker is 23-24m, does anyone question about their maneuverability by its size? No, f-22 and su-35 are always been regarding as two most maneuverable fighters in the world.
For j-20, I saw many different version but most are various from 20-20.5 m which makes it not ridiculously long/large I will say, so why this is an issue matters here?
BTW, what is the size of j-20 exactly? Seriously, this is a genuine question asked here... Is there a concert answer/analysis or anything now?