https://nwn.fandom.com/wiki/Uncanny_dodge
Basically if you're in combat and something tries to sneak attack you, if your effective level is 4+ levels higher than the attackers effective levels, you do not get flanked (sneak attacked).As of Enhanced Edition patch 1.74, uncanny dodge II grants immunity to sneak attacks from a flanking attacker unless the attacker has at least four more combined class levels of rogue, assassin, barbarian, and shadowdancer than the defender.
If you're still caught flat-footed, you will be hit with a sneak attack like normal regardless of your "effective level".
As this is a pretty impactful change of EE that has, at least to me, went previously unknown I wanted to make sure everyone knew about it. Cheers!