How different would the movie have been?

We'd see Iron Mans butt

Not as good honestly. For me at least. I liked how the film catered to my nostalgic inner child throughout the entire film.

In terms of events, probably a lot of blood, Captain America’s actual butt, sex jokes made mostly by Ant-Man and possibly Captain Marvel constantly running her mouth about how she’s being treated unfairly by the rest of the team simply because she’s a woman (and not because she’s literally a complete stranger) which ends up causing Thor to go for the head and immediately end her reign of terror in the MCU.

Noobmaster69 would make sexual insults.

Peggy and Steve sex scene.