Well they have been transitioning into more a “3-4 base” the last couple years but i think that had more To do with coughlin being involved. Their drafts the last handful of years point to lack of continuity between GM/President/HC.
At their best like in 2017 (10-6 lost in AFC Champ Game) they were a four man front scheme and according to WAR.. they were one of the best defenses of the decade which isn’t surprising given their success with probably the worst starting QB in the league. I’m pretty sure every pro bowler from that team is gone now which again points to distinction in terms of roster building. They have been trying to be more “multiple” which is never a good thing because it usually means (in this case it’s true) you don’t have the personnel to have an identity. Ie: the team who’s trying to be the most “multiple” this year on defense was the cowboys. The teams that have an absolute identity (49ers, Steelers, ravens, colts...etc) are the best defensive teams. Another example: deforest Buckner was a great DL for the 49ers last year.... they traded him to the colts Bc they felt he was too light to play the technique they drafted kinlaw for. Buckner has been great for the colts. 49ers defense is still very good despite their injuries.
Offense: spread power run which is imo is the best offense to run in CFB because you don’t have to have a great QB but in the event to you do find one... their ceiling can be elevated even if they don’t have elite nfl arm talent.