My two texts are Waiting for Godot by Beckett and A Streetcar Named Desire by Williams. Which elements could I compare and contrast for my English...

I don't know exactly what the nature of your assignment is, but generally in literary criticism the more specific the better. I would not focus on all of these topics. I would pick one and do an in-depth textual analysis. I wouldn't focus on props; there are some in the scripts, but for the most part that will be the choice of the director. 

Symbolism could be a good topic, but I would encourage you to be more specific. Maybe find how symbolism affects a particular theme, for instance, how does the symbol of Godot compare to the symbol of Blanche's dead husband? Both characters do not appear on stage. Both represent a certain type of meaning or fulfillment that is absent from the play. This is only one example. The key is that rather than vaguely discussing a particular literary device, such as symbolism, you hone in on a particular use of that device and support it with textual evidence. The way that meaning is created would be a good choice as well. Once again, be specific. You could discuss how both plays show signs of nihilism and loss of meaning. In Waiting for Godot, the main characters wait endlessly for a character who never comes; in A Street Car Named Desire, Blanche struggles with the loss of her husband and job. In both cases the characters find themselves in a position that is seemingly devoid of meaning.

I hope this was helpful for your assignment. The more practice you get with getting specific and focusing on the text the better you will get at it. Good luck!