The CEO has a hand in everything that the company does and they make both small and large changes. The last CEO was responsible for the initive that encouraged employees to talk about race with thier customers, an initiative that customers notice and that backfired horribly and in a unexpected way.
No, I don't think the average customer will notice any changes at Starbucks, at least not immediately. Over time the new CEO will try new things: new products, new pricing schemes, new store decor, new partnerships with other brands. But these changes will happen gradually, and I feel they would be implemented without disrupting the main focus of the brand, so people won't really notice anything different.
No, the average customer will not notice any change due to Starbucks hiring a new CEO. People who go to Starbucks regularly will still be able to purchase the same coffees and specialty drinks that they always have. If he is smart, the new CEO will not interfere with a successful strategy.
No, the average customer will not likely notice any change with a new CEO running Starbucks. Most customers are not even paying attention and probably will not know that there is a new CEO. As long as they can still get their favorite flavors from their neighborhood Starbucks and the same price they are used to, they will be happy.