I saw the musical in London in 1987 (and Phantom 2 months after it opened in 1986). There have been changes in the lyrics over time, as I noticed in the 10th and 25th anniversary versions. Not a big deal to me. A reason was found to change things. And yes, Gavroche's "Little People" ha shad more changes. Maybe it was determined that it slowed the pace too much right then, and that outweighed the need for character background.
As for performances, anyone watching the anniversary DVDs will see differences in style. Each performer gets to, and needs to, put himself into the role to make it his own. I don't have a problem with Crowe's performance; he's an actor known for giving his all. This is his, and the director's, version. I personally enjoy different interpretations. And Javert's supposed to be rigid, especially at the beginning--only someone that stiff will become obsessed with Valjean and then have the fall he has when his rigid rules are upended.
I've read that, since the actors didn't have to sing to each the last row, and were singing on set, they got to put more emotion in.
I am SO looking forward to this, but Hubby is working Christmas Day, so we'll have to wait.