Yes 4-5 inch would work for corners and the straight lines. 10 feet is for both t posts and wood posts.
Basically an H brace is a twisted wire that goes from the top of the post to the bottom of the post. If a horse was running around or pawing there or kicked out, his leg could get stuck between the brace and the fence or get twisted up in the wire. I don't get any frost or snow here which is why we sunk the posts 2 feet into the ground. Good luck!
“Good things come to those who wait… greater things come to those who get off their ass and do anything to make it happen.” - Unknown