Manuverability comes in many forms, Trust to weight, TVC, canards, and overall geometry of the aircraft. Something like canards may pose a problem for an aircraft the same can be said for traditional nozzles, how much if any do these factors contribute to RCS depends on which aircraft we're are talking about, or in other words each aircraft is different even if, for instance, they both have canards.
I'm not familiar with what China has been working on in terms of jamming capability and EW but Sukhoi aircraft use the KNIRTI SAP-14 jammer and the SAP-518 ECM pod these are said to be quite good. You also have to remember that much of the avionics on a Russian aircraft or any aircraft whether it's American or Chinese is not made by the aircraft manufacturer but a company that usually specializes in a particular feild such as radars, or engines. Sukhoi tries to produce the best aircraft they can and equipe it with the best avionics available to them. The companies that produce these avionics usually only specialize in a few fields or only one field, so naturally they do the best they can because if they don't no one will buy from them. This is not to say that Sukhoi does not develope systems for their aircraft but that rather sukhoi and all other major aircraft companies have subcontractors that provide them with avionics.