Ackermann
The geometry that makes the inside and outside front wheels point at different angles through a turn, because they are tracing circles of different radii.
In a normal turn the inside front wheel has to point at a sharper angle than the outside one, because it is tracing a tighter circle. Ackermann is the steering geometry that arranges this, and factory cars are set up for the small steering angles road driving uses.
A drift car does not use small angles. At 60 or 70 degrees of lock the factory relationship between the two front wheels is nowhere near right, and the result is that one tire is fighting the other - which scrubs speed, generates heat, and makes the car feel like it is binding at full lock.
Why it matters to your build
Adjustable Ackermann is one of the main things that separates a designed angle kit from a pair of cut-and- welded knuckles. Cut knuckles give you lock; a kit gives you lock with the geometry corrected to suit it. That is most of the price difference, and it is why published guidance on angle kits talks about Ackermann, caster and toe adjustability as the markers of a quality kit.
Anti-Ackermann is the setup many drift cars actually run: the relationship reversed, so the *outside* wheel takes more angle. At drift slip angles that can put more load on the outside front tire, which is the one doing the work. Whether it suits your car depends on the kit, the tires and the surface - it is a tuning choice, not a universal improvement.
What you will notice if it is wrong
Steering that feels like it is binding or going heavy at full lock. Front tires scrubbing and overheating. The car understeering at high angle when it should be holding. And the classic symptom of any unaligned angle kit: the car behaving differently turning left and right.
Where it sits in the build
Phase 2, alongside the angle kit and the alignment that has to follow it. There is no point setting Ackermann before the kit is on, and no point fitting the kit without setting it afterwards.
Questions
Should I run anti-Ackermann?
It is a tuning choice rather than an upgrade. Many drift setups do, because at high slip angles it can load the outside front tire more usefully. Start from your kit manufacturer’s recommendation and change it based on tire temperatures and wear, not on a forum post.
Do cut knuckles have adjustable Ackermann?
Generally no. That is the main functional difference between a $200 pair of cut knuckles and a $1,500 bolt-on kit, and it is why the kit is worth it once you are chasing consistency rather than just lock.