Wider Stance, Knees Outward, Feet Flared Out
Of course the deadlift isn't a squat, but one can get their hips much closer to the bar, and you much more quad drive by pushing the knee's outward with flared toes. This is where I find my strongest position, feet just outside arms. One of my powerlifting buddies commented, you're doing Ed Coan's Stance.
This "Pseudo-Sumo Deadlift (Coan, Squat-Stance, StrongFirst Deadlift, etc) decreases the loading on the Back and places more loading on the Quads.
Even more importantly, Wider Stance with the Toes Flared Out Deadlifts or Squat, engages the Glutes to a much greater degree. The Glutes are the largest muscle of the body.
Yes and No
I think the more similar your squat stance is to your deadlift, the better off you are. This is a bit unfair to conventional pullers, however, as a high bar squat may be their best bet, as was the case with Knostantin.
Yes, there is definitely some carry over if your Squat Stance is similar to your Deadlift.
Essentially, your Squat becomes an Auxiliary Deadlift Exercise and your Deadlift becomes an Auxiliary Squat Exercise.
As I have posted before, one of the keys to increasing Limit Strength in Competition Lift is with Auxiliary Exercises (Research Dr Tom McLaughlin, Anecdotal Training Data-Westside Powerlifting Training Method).
On a personal note, I am a Conventional Deadlifter.
Years ago, in a training session I preformed a heavy Competition Squat single. I ask my training partner if I broke parallel. His reply was that I broke parallel twice with one repetition; which made no sense.
I ask how that happened. His reply was your leg broke parallel and you lower back did to!
My Squat was more of a Squat-Good Morning. No wonder I stop Deadlift for months and still come back and pull some heavy Deadlifts.
The same is true for Sumo Deadlifts and Squat-Stance Deadlifts.
However, here's the...
The Squat and Deadlift are two different movement. However, the same muscle groups and similar movement pattern are train.
Thus, it is easy to overtrain the muscle groups (especially the back) when performing a highly intense, heavy Squat and Deadlift training session in the same week.
One method that can minimize training the Squat and Deadlift heavy in the same week is...
1) Narrow Stance Squat with Sumo Deadlift
2) Wide Stance Squat with Conventional Deadlift
For a number of years, I trained and competed using a Wide Stance Squat and Conventional Deadlift.
The Wide Stance Squat minimize the loading on my Back (no more Squat-Good Mornings), allowing me more recovery time for my Conventional Deadlift. I posted some personal records with my Wide Stance Squat an Conventional Deadift.
However, the Wide Stance Squat isn't something that feels natural to me. Every time I Wide Stance Squat, it feel like a new movement. I have to focus to a much greater degree on my Wide Stance Squat Technique
The Narrow Stance Squat feels more natural.
High Bar Squat
High Bar Squat are a Quad Dominate Exercise; a somewhat good Low Bar Squat and Sumo and Conventional Deadlift Auxiliary Exercise.
A much more effective Sumo and Conventional Deadlift movement is High Back Quarter Squats. The Quarter High Bar Squat needs to be performed from the same Quarter Squat position that you are in for your Sumo, Squat-Stance and Conventional Deadlift.
Other Good Quad Dominate Deadlift Exercises
1) Quarter Front Squats.
2) Quarter Step Up
3) Partial Leg Press. Gene Bell, one of the greats Deadlifters in the 220 lb and 242 lb weight class, stated the Leg Press was one of his most effective Deadlift Assistance Movements.
There many other good Compound Quad Exercises.