The burst and full auto modes on weapons are technically bursts, differs only ap cost, spread, onehex, range and bullets in burst, the supression is a perk on burst weapon that gives 3% chance to EVERY bullet that u fire from your weapon to supress a target, even if the bullets didnt hit it, but the target were in the weapon range cone, the supression perks are stackable.
no criticals at all, supression effects are independent from criticals, no knockdowns or ko's.