Two different things. The correction brackets correct caster. The track bar keeps the axle centered. The AEV 3.5 lift raises the front track bar and flips the drag link. Raising the track bar 3" positions the axle pretty close to center.
So NO ... You don't really need a adjustable track bar.
I've had both the 3.5" and 4.5" AEV kits and the brackets do correct the geometry of the track bar for the most part. The axle still swings slightly towards the chassis pivot side slightly over 1/2"; not enough to justify the expense of an adjustable track bar unless your are very finicky about your suspension. The longitudinal shift towards the center of the Jeep is more noticeable without adjustable control arms.
A forum community dedicated to Jeep Wrangler owners and enthusiasts. Come join the discussion about reviews, performance, trail riding, gear, suspension, tires, classifieds, troubleshooting, maintenance, for all JL, JT, JK, TJ, YJ, and CJ models!