I cant say ive really noticed an impact of form IQ
i mainly run SG but will use other formations too.
defensively i mainly use 3-4 but lots of 4-4 and some other formations too.
i only train SG and 3-4 FORMIQ for both is in the 40's typically, and havent seen anything that i can point my finger to as a negative impact of using any other formation on O or D (FORMIQ usually around 10-ish)
moreover, i dont seem to notice anything overly positive coming for SG or 3-4, i still get gashed for big plays on D or bled by lots of little ones.
on O just earlier this year I had a stretch of games where i think i threw 13 INT in 3 games, moslt all of them were me out of my SG with high FORMIQ and usualkly going against D/N for them with a relative low FORMIQ.
so i am not prepared to completely give up training formations all togetehr but i seriously doubt it has very much impact after you consider personelle differences first and gameplan second.
i suppose it could come into play as a distant tiebreaker but for the most part i think an outcome of a game is decided: