Bet Sizing Tree Design: Small Bets, Large Bets, and Overbets

Short Answer
Bet sizing answers one question: what price should villain face with the continuing range? Small bets pressure weak holdings, large bets polarize, and overbets require a strong nut distribution.
Small Bets
Small bets fit boards where the bettor has broad range advantage without an extreme nut edge. They deny equity cheaply and let medium-strong hands bet at higher frequency.
Large Bets
Large bets need polarization. The value side must tolerate calls; the bluff side should block continues or improve on later streets.
Overbets
Overbets are not intimidation. They force bluff-catchers to defend against a high price when the bettor keeps more nut hands and villain is capped.