MP1 is most faithful to the book and the characterization of Fanny Price is to my mind true to the book although other will disagree. It is also worth watching MP2 1999 with Francis O'Connor as Fanny Price. Its emphasis is very different but you should see enough of the plot of the book to accept that it is Mansfield Park and to my mind it's the best film version of a Jane Austen novel although I'm certain others will disagree. I wouldn't bother with MP3 2007 with Billie Piper, the characterization of Fanny Price is neither faithful to the book nor of much interest. I should say I don't particularly like Fanny Price as characterized in the book or MP1, but I do like her as portrayed by Francis O'Connor in MP2.
As for the other characters, I think Jackie Wood Smith's performance as Mary Crawford in MP1 is spot on, Samantha Bond turns in a good performance as Maria and while Anna Massey does a good job as Mrs. Norris, Sheila Gish (MP2) is the better by a head. Let me know what you think