1. You may notice that Mr. Greenberg (Felix Bressart, a staple in Lubitsch movies of this period), the Jewish actor who gets the role of his life toward the end of the picture, is never explicitly referred to as Jewish; even Shylock's big speech from The Merchant of Venice, which Greenberg recites at several key points, is stripped of the word "Jew" every time he recites it, And the film never explicitly says that the Jews are a particular target of the Nazis, even though the climax of the film depends on just that fact.
Hollywood movies rarely included Jewish characters in this era, and anti-Nazi movies were de facto forbidden from mentioning Hitler's targeting of the Jews; the only American movie that did so was Warner Brothers' Mr. Skeffington, where the title character tells his daughter that he is not safe in Europe because he is Jewish. And as this article explains, that one line brought the movie under attack from all sides:
Even that single instance caused Jews of a certain stripe--for example, those who governed the American Jewish Committee and the Anti-Defamation League--to have fits, and Roosevelt's own Office of War Information sent in an official complaint: "This portrayal on the screen of prejudice against the representative of an American minority group is extremely ill-advised."
So To Be Or Not To Be, like most anti-Nazi films of the time, emphasizes the general aspect of the Nazi terror -- the threat the Nazis pose to everyone -- rather than the threat that they pose to a specific group. Still, the movie finds ways to send out signals about the latter threat, mostly through Greenberg; after the montage of posters showing the mounting reign of terror in Poland, Lubitsch dissolves to Greenberg reciting: "If you prick us, do we not bleed?"
And one thing that may or may not have been intentional, but certainly makes the same point in its own way: after his climactic recitation of Shylock's speech, Greenberg disappears from the movie. He's not seen on the plane with the escaping actors, and he's not seen among the actors after they've escaped to England. We're never told that he didn't escape with the rest of them, and I think we are supposed to assume that they all got away, but we never actually see him again after he stands up to the Nazis. For all I know this might just mean that Felix Bressart wasn't available when they shot those scenes, but it does make a subliminal point, intentional or no, about which member of the troupe is the least likely to get away from the Nazis.
2. In Carole Lombard's biography, Screwball, it's mentioned that the part of Maria Tura was actually intended for Miriam Hopkins; she was one of Lubitsch's favorite actresses (she gave three superb -- and very different -- performances for him, in The Smiling Lieutenant, Trouble in Paradise and Design For Living); her career had started to falter, due in part to her own hotheadedness and unreliability, and To Be or Not to Be was to be her comeback. However, Hopkins objected to the fact that her part was clearly secondary to Jack Benny's, and lobbied Lubitsch and Edwin Justus Meyer for a rewrite to make the part bigger; meanwhile, Lubitsch was unable to get a Hollywood studio to take on the project and was having trouble raising the money to make it independently. When Lombard heard about the project and read the script, she agreed to take the smaller role (in exchange for bigger billing); Hopkins withdrew, and with Lombard's name attached, Lubitsch and Alexander Korda were able to raise the money they needed to make the film.