Both Main Character and Impact Character may grow in a Grand Argument Story, though only one will have a fundamental paradigm shift and Change. In Kramer v. Kramer, the father goes through a life change from disconnected to loving parent. His son is the Impact Character. The wife is part of the Overall Story throughline where it looks like a custody battle but it is really about a family power struggle. She doesn't change per se but gives up the battle--something easily within the bounds of the Overall Story throughline (especially if it is a Manipulation/Psychology domain). If it is two stories (with the wife's personal journey outside of the family unit as a substory), then you would create two storyforms: one for the main story and one for the substory.
Sex, Lies & Videotape DEFINITELY has multiple stories going on. Create a storyform for both of them. Scent of a Woman and Passion Fish are both clear grand argument stories. In Scent of a Woman, Charlie is the Steadfast Main Character and Lt. Col. Slade is the Change Impact Character. In Passion Fish, Mary-Alice is a Change Main Character and Chantelle is a Steadfast Impact Character (though I think there may be a substory with Chantelle and her daughter). They both involve physically and psychologically damaged characters that Change and come back to 'life.'
As far as Lethal Weapon 1 goes, Riggs (Gibson) is clearly supposed to be the Change character and Murtaugh (Glover) the Steadfast character. It's a little confusing who the MC is supposed to be since we see the personal side of each and the relationship throughline is emphasized more than both. I 'think' it's supposed to be Riggs. Much of Murtaugh's personal life is tied to the Overall Story throughline involving the smuggling ring. The fact that Murtaugh feels he is still useful hardly constitutes a paradigm shift in my opinion. It does look like character growth, however.
Freaky Friday seems to have two stories going on: the mother's and the daughter's. They are placed within the framework of the body switch and the mother's impending wedding to someone the daughter doesn't like. My thinking, if I remember the story well enough, is that it seems that the Overall Story is about the mother getting married and her daughter's fight against it. On that point, the daughter appears to let go of her concerns and join back into the family which suggests she's a Change character. Mom grows to appreciate her daughter's musical talent, but that seems (to me) more like character growth than a fundamental paradigm shift.