Hi Francisco. Thanks for your answer. It is always nice to see another enthusiasist of fighter designs :D
Current best aerodynamic Russian design would be Su-35 and Mig-35 series, itself not having canards should pretty much be free from the penalties of trioplane approach.
In fact in T-50 (PAK-FA) they are using “moving vortex generators” instead of canards that pretty much has positives of canards but not the negatives (drag etc.)
Also as far as I know Su-27 had negative stability (in fact it had the first operational Russian fly-by-wire system) and from Mig-29M onward Fulcrums series also had negative stability and fly by wire (they displaced the engines to the back a bit which sifted center of gravity quite away from lift center, making it unstable)