I believe the term "impact player" is over used. Much like the term/phrase "the next (name that player; this year Dak Prescott)". And I don't buy all the descriptions of prospects when it comes to projecting their NFL career. If those things mattered as much as desire, heart and will, there would be no busts. Which is another term that's overused. They're "busts" because the evaluation on them said one thing and they performed to a far lesser degree.
But I don't know if the term "impact player" can be defined. As it is used, I'd say somebody who has a distinct affect on the outcome of a game, game after game. Aaron Donald is an impact player. Von Miller is too. Antonio Brown has been the last 4 years; 6th rounder by the way. Luke Kuechley is too. But coming out of college to be an "impact player" from the get-go? Few and far between.
How do the Rams stack up against other teams? Well they have Donald so I'd say, about the same. Who has a wealth of impact players?