See this and the rest of the M18 series:
https://youtu.be/7AuYaGuuYrs.
Previous years' breakdowns of Kia's T2 scheme are also really useful.
Here's a breakdown I made in my own notebook that distills the insights of his multi-part M17 T2 series:
Preferred base fronts:
* Under: base for run situations
* Over: base for pass situations, leaves A/B gap bubbles susceptible to power run schemes
Special fronts:
* Normal: zone blitzes, yolo blitzes
* Wide 9: stretch stopper
Cover 3 Cloud:
* Hard flat to solo side
Cover 6:
* Mix of quarters and cover 2
* When ball is on the hash, places little stress on the corner in flat zone to short side
* To bracket strong receiving threat w/ corner to single side in flat zone and safety over top
* Quarter flat coverage looks good for TE corner (test)
Cover 9:
* Inverted cover 6 with flat zone corner to receiving strength/trips side
* flat corner in a soft squat not hard flat—will drop rather than jam and redirect as the cover 6 flat corner would
* better vs. trips?
Cover 2 Books:
* DAL: Every cover variation possible
* DET
* NYG
* PIT
* STL
* TB
Cover 3 Books:
* ATL
* JAX
* SEA
Mixed:
* CIN
* MIN
Specific Play and Coverage Notes:
Tampa 2: Deep sideline to flat coverage, NOT flat coverage
* Cloud flat obstructs release, funnels WR inward toward S
* Vert hook matches vertical seam, rally to underneath plays second; late to rally down if no vertical threat
* Mid read by MLB
* For trips, spotlight #2 WR matched on vertical hook zone for extra depth/carry on vertical routes
* Can create trap coverages by routing flat zone CB to a deep 2 and a deep S to a hard flat (for playmaking S)
* 3rd or 4th and 10 or less
Cover 2 Sink:
* Soft squat by CB will have CB bail and not contest release; can pattern match if no other threat is present; vs. vertical will prioritize vertical route
* Longer than 3rd or 4th and 10
* Good vs. corner routes (smash)
Cover 2 Carry:
* Cloud flat CB assignment
* Traditional cover 2 w/ MLB in shallower zone than Tampa 2; 3 REC hook assignment for MLB
* MLB will match 3rd receiver on a vertical route
* 3rd and 4-5 defense
* Red zone D
* Good vs. slants, Texas, Mesh
Cover 2 Hard Flat:
* MLB has Tampa 2 run through
* Good vs. shallow crossers (mesh)
Cover 2 Drop:
* Soft squat assignment can convert to man vs. certain alignments
Overload 3, Show 2 (Dime Normal):
* Good sack/fumble inducer
DAL-Specific Formation Notes
43 Over:
* Cover 3 Match here, not in other 43 sets in DAL
Quarters 3 Deep:
* Cover 1 contain: Great for man coverage + 2 robber S for 3rd and 5, inside the red zone