So i played the hoth campaign, and regular riots got 2 block power tokens each. If i attack, who decides when they are spent and if they spend more than one?

Imperial figures always spend all their applicable power tokens at the first opportunity.

LotA rules, p.21 POWER TOKENS

· When an Imperial figure declares an attack, it spends all <damagept> and/or <surgept> tokens it has. When an Imperial figure is declared as the target of an attack, it spends all <blockpt> and/or <evadept> tokens it has. This means Imperial figures can spend more than one power token in an attack.

· While an Imperial figure has two power tokens, it cannot gain any more power tokens.