the booties are one size a larger needle 2/3 will make a little bigger bootie, 0/1 a smaller size.
I use a blend of Angora and Merino any where from 60/40 to 80/20 so the angora retains it’s halo but the merino gives it strength. All angora works also. The blended angora comes with more yardage than 100% angora so it is more reasonably priced to knit as you can usually get 3 to 4 booties out of a skein.