I believe that the setting you have should be okay as long as you realize that the map will be 8 inches x 8 inches if printed out 1:1. As long as it doesn't slow down the computer you should be good. Now, in order to know how much detail you can put on that map, try and figure out a scale (ex. if the map is 2400 miles north/south, then 1 inch equals 300 miles and each pixel is 1 mile) and that would tell you what you can do as far as details go. Using that example, most small towns would fit inside the 1 pixel and would most likely be represented abstractly if at all (either way is good, just be consistent - maybe showing important towns but not necessarily all of them). All this to tell you that a scale goes a long way to making a believable map.