My son emailed one professor who he’s communication with over the last year to tell him he was going somewhere. The professor was so gracious, sent his congratulations and then said (I paraphrase) that “he’s been in the business for 30 years and he knows that some of his favorites are other people’s favorites too.” The rest of the schools, he just went into the portals to decline the offer, for one school, we had to return a postcard with the decision.