Found a plausible solution if anyone was wondering.
Inside C2:
1 - System > compare two values > WindowWidth (greater than) [your max window width]
1 - System > compare two values > WindowHeight (greater than) [your max window height]
Action > set Canvas size [your max window width and height]
outside of C2 (once your project is exported) you can add -[amount of px you want as padding]
Query(window).resize(function() {
cr_sizeCanvas(jQuery(window).width()-25, jQuery(window).height()-25);
});
for percentage of the screen, bracket and times by the percentage as a decimal (this is 90%):
Query(window).resize(function() {
cr_sizeCanvas((jQuery(window).width()*0.9), (jQuery(window).height()*0.9));
});