Whatever spot gives you the most eastern sun is what you want. You also need to prune peach trees nice and open to increase ventilation- also to assure peaches and there nearby leaves get adequate light as well as the new shoots that will carry fruit the next year. Peaches require a lot of nitrogen compared to apples and pears- they don’t die until they lose their vigor and N. helps them maintain vigor- as does the turf free circles already mentioned. I have a 25 year old Madison that is still as vigorous as a young tree and I manage what I believe to be a Cresthaven that must be 50 and still cranks out hundreds of pounds of absolutely delicious peaches. I’ve also had lots of younger peach trees die of old age.