About river bet
Alright, river is the last street, soul crusher or the opposite, the last card that make players to win big or loose, to survive in tournaments or get knocked out.
Good players try to remember hand history street by street, what makes bluffing them very hard and also they can bluff into good thinking players, where you can represent big hand by flop/turn/river scenario you played. Leveling is the most interesting detail, and at the river we can also see very strange calls/ shoves/ reshoves etc. , mostly by strong players, but not everytime
Action on the river is very depending of opponent player level: you can bluff like almost or you can't never, it is very, very polarised or not etc.