Inquisitive FAQ
How does Inquisitive interact with Sneak Attack?
Insightful Fighting creates an alternative way to satisfy Sneak Attack. Once the contested Insight check succeeds, you can Sneak Attack that creature for the feature's duration even without advantage and without an ally beside it, as long as you do not have disadvantage. All ordinary once-per-turn and qualifying-weapon rules still apply.
The base Sneak Attack rule still applies
Insightful Fighting adds a special Sneak Attack route against one studied creature. After winning the Insight-versus-Deception contest, you no longer need advantage or a nearby ally against that target, but disadvantage still prevents Sneak Attack.
Subclass interaction
Insightful Fighting creates an alternative way to satisfy Sneak Attack. Once the contested Insight check succeeds, you can Sneak Attack that creature for the feature's duration even without advantage and without an ally beside it, as long as you do not have disadvantage. All ordinary once-per-turn and qualifying-weapon rules still apply.
Reaction attacks can still matter
Off-turn qualifying weapon attacks can still use Sneak Attack because the base feature is once per turn. Insightful Fighting can remain relevant to those attacks while its duration continues and its conditions are still met.
Do not double-count subclass damage
Eye for Weakness adds extra damage to Sneak Attack against the creature affected by Insightful Fighting. It enhances that Sneak Attack rather than creating a second independent Sneak Attack on the same turn.