I've seen N2N twice from row H in the mezz - terrific, no problem. I'll be there several more times, I'm sure.
As for HAIR: it's a bigger theater, and therefore you are further away from the stage, but the sight lines are fine. And yes, several times during the show, when cast members go into the audience, they do indeed go into the mezz. In fact, one of the important factors in selecting the theater was the fact that they could very easily and quickly access the mezzanine from the stage via the boxes.
2016 These Paper Bullets (1/02) Our Mother's Brief Affair (1/06), Dragon Boat Racing (1/08), Howard - reading (1/28), Shear Madness (2/10), Fun Home (2/17), Women Without Men (2/18), Trip Of Love (2/21), The First Gentleman -reading (2/22), Southern Comfort (2/23), The Robber Bridegroom (2/24), She Loves Me (3/11), Shuffle Along (4/12), Shear Madness (4/14), Dear Evan Hansen (4/16), American Psycho (4/23), Tuck Everlasting (5/10), Indian Summer (5/15), Peer Gynt (5/18), Broadway's Rising Stars (7/11), Trip of Love (7/27), CATS (7/31), The Layover (8/17), An Act Of God (8/31), The Curious Incident of the Dog in the Night-Time (8/24), Heisenberg (10/12), Fiddler On The Roof (11/02), Othello (11/23), Dear Evan Hansen (11/26), Les Liaisons Dangereuses (12/21) 2017 In Transit (2/01), Groundhog Day (4/04), Ring Twice For Miranda (4/07), Church And State (4/10), The Lucky One (4/19), Ernest Shackleton Loves Me (5/16), Building The Wall (5/19), Indecent (6/01), Six Degrees of Separation (6/09), Marvin's Room (6/28), A Doll's House Pt 2 (7/25) Curvy Widow (8/01)