All of these are before 2020 but The Heirs ticks all those boxes, otherwise, as does Kurosaki-kun no Iinari ni Nante Naranai. Also the other versions of Boys Over Flowers (China's Meteor Garden and Thailand's F4 Thailand: Boys Over Flowers).
Mountains and Ocean has opposite personality/social class leads and a heavy love triangle. Also, My Deskmate (extrovert non-famous not good student FL/introvert famous good student ML and a love triangle. I don't remember the ML being really possessive, but I could be wrong.).
Click Your Heart is fun in that there's four choices for the FL, some of which are the complete opposite to her (like the bad boy) but YOU get to pick who she chooses.
Also, these have a couple of the things you want and are more recent: A River Runs Through It (the leads are complete opposites in personality and there's a love triangle in a sense - the FL likes SML while ML likes her. ML isn't possessive, though.) Crushes Reverse has a love triangle but nothing else, and Time and Him Are Just Right (smart, introvert ML/extrovert FL, but no love triangle),
