Depends what we mean by "the Northern Soul scene"?
There are four distinct era's and generations of youths as I see it,
The 60's lot, the 70's, 80's....and the current young souls, (excluding the over 40' newcomers based on age).
Common denominators are the music the club culture, dance styles and the collectors.
Differentials could be the fashion and the extent of the digging?
....Then there's the question of what constitutes being a mod?
Being a bit of a hybrid,( my own youth began on the tail end of the early 70's "scene" and ran into the the begining of the 80's era....so I was too young to be a 60's mod and too into new rather than retro fashions to be a Quad' Mod.
Don't recall many Mods of either ilk being around "the scene"in my youth.
The original Wheel boys from our way got to an age and hung their boots up, the original early 70's lads did the same.
In my experience, a lot of the early 70's boy's background was bootboy rather than mod.
The continuity seems to stem from the clubs and the guys providing the music and the evolution of the same.
To me, the core of the scene as I understand it, is the club culture and the music, rather than the variants of tribal styles of those who have populated it over the years.
So my own little perspective is that the Mods, 60's or Quad, are not responsible for what I understand to be the NS scene per se, but the 60's Mods were the pioneers of the club culture and of the appreciation of "deep soul with a dance beat", (to quote RS), which were subsequently adopted and reinterpreted by the succeeding generations.