Obviously all offensive linemen are important to a good run game, but I'd imagine some schemes demand a good player at one position more than others? For the inside zone, I'd imagine you need a good center and running back who can read where the cut is before anything else. I'm think back to when the Falcons picked up Alex Mack and had Devonta Freeman. The rest of the offensive line was decent at the time, but those two guys really made their run game and inside zone scheme really go, or at least that's what it seems like. Video suggestion: how about the Patriots defense, particularly with picking up guys like Judon and Mills in the offseason and Phillips last year? I feel they've quietly been the most consistently good defense in the entire league. Whether it's a bottom shelf offense like the Jets or the Bucs and Cowboys, they've competed hard against everyone.
Centers are super underrated. If you have a guy there that can take on shades or nose tackles on his own, it frees you up to do so much stuff inside. I'll add the Pats to the list. I haven't taken a look at Belichick's defense for awhile, but you're right. They've been limited on personnel and always find a way to produce with guys that they pick up off the street or with signings that don't make the headlines.
Does inside zone differ from iso/dive in the fact that it blocks different & the RB chooses the hole based off the read, instead of having a pre-determined hole?
