I do not know well Phantasmagoria runs on modern computers, since it uses the newest version for the SCI engine Sierra ever made, and so far that SCI version has always been buggy on me in other games written in it. The game uses real actors, so that girl that is you is portrayed by a real actress, however the graphics hardware of the time wasn't fully ready for that, and thus they had to convert that to 256 graphics, and they used the highest resolution they could back in the day, hence the need of seven CDs. Although gameplay wise the game is a bit flawed, the horror mood was definitely kept well, and the finale is quite heavy, and I must say the ending when you finished the game is quite realistic.
One thing I gotta warn you about in Phantasmagoria. During the finale you have very little time and a lot to do an one mistake and you will die and your savegame will get deleted (only happens i f you die during the finale. If you die earlier you can still reload a savegame). I don't really know what Sierra was thinking there. When it comes to the story Phantasmagoria is actually a recommendation if you love horror.
Now it's hard to imagine given the sweet looks of the King's Quest series, but Roberta Williams is said to be a horror fan.
And yeah, I agree that with Alice the art direction and voice acting was indeed spot on. Now Alice herself was already portrayed wonderfully by her voice actor, but the guy who voiced the cat nailed it completely. ;)