Sadly, Orient Beach is not the same since hurricane Irma. We were there for a day in 2018 (the anniversary of the storm) and it was very quiet. The non-nude end looked even quieter. COVID has probably made things even worse.
We were at Orient, in front of the former Club O a year ago. There were many people, but we had no trouble getting chairs. Not at all like it was before Irma. We were also there the day the BN cruise stopped and that was really crowded. No worry about getting a chair that day, there were none to be found. The most crowded beach that we've been on is probably Half Moon Cay when the BN cruise stopped there. I've never been around that many nude people, and that's counting the Spencer Tunick installation I did.
Half Moon Cay would be a perfect answer to the OPs question if it were nude beyond when BN cruises stop there. I mean, a nude beach with a pirate ship shaped bar right in the middle! With 2500 nudists on it. Our favorite nude cruise stop.
We were on that nude cruise that stoped in SXM so we had the inside info not to go to Orient that day. We met others that didnt know the BN ship was in that day and were glad they decided to pick that day to go on the nude speedboat cruise around the island. We met them again in June at Club O and all had a much more relaxing week. Willie the bartender remembered the day of the cruise but she didnt have fond memories of the experience.
Not sure about biggest crowd, but Little Beach on Maui, Hawaii was fairly busy. Much busier on the Saturday afternoon we were there but even the Tuesday we visited had substantial crowds. Still loved this beach very much.