where can we find a list of these planned essays?

Here, I’ll just copy-paste from the Kickstarter page:

@$500 pledged: bonus essay on elections in ASOIAF (the Night’s Watch, the Ironborn Kingsmoot, etc.).

@$1000 pledged: bonus essay on George R.R Martin’s influence on the deconstructivist fantasy subgenre (think R. Scott Bakker, Joe Abercrombie, etc.).

@$2000 pledged: bonus essay on Maurice Druon’s Accursed Kings series, the historical novels that George R.R Martin credits with inspiring ASOIAF.

@$3000 pledged: bonus essay series examining George R.R Martin’s Dunk and Egg stories, and what we learn about the history of House Targaryen and the Blackfyre Rebellions from these stories.

@$5000 pledged: bonus essay series covering the Great Councils of Westeros, their historical parallels with the rise of Parliamentary government in Medieval and Early Modern England, and how the history of Westeros could have changed dramatically had the votes gone the other way.

@$8000 pledged: bonus essay series on the Politics of the Seven Kingdoms. Seven essays examining the historical and political development of each of the Seven Kingdoms, their internal political rivalries, and their unique strengths and weaknesses as polities.