I thought that I would provide a few words about my experience with the Samui+ program since I just got back.

Booking and SHA certificates:
We chose The Lamai Samui for the first week and it was very easy to just email them for the SHA Extra Plus certificate required. The next 3 nights were planned to be at the Conrad, after which I would fly home. Also no problem getting the SHA certificate from them and I was able to apply for my CoE and was applied within a few hours I think. My partner however was going to stay a few more days and wanted to island hop up to Koh Tao for some diving. Based on the ferry schedule, she tried to book a hotel near the pier for one night and then would ferry to Koh Tao the next day, so she ended up with a few hotel bookings which provided her with SHA certificates. When she applied for her CoE though, it was rejected. We couldn't find this information published anywhere, but apparently you can change hotels one ONCE during that second week even if you are only booking SHA+ hotels. By this point we were 3 days from our departure flight, so I just panic booked the Renaissance for the entire second week because they had a great rate for 7 night stays. Got the SHA certificate from them and she was then able to be approved for her CoE.

This meant that I had a CoE for the Lamai and the Conrad and she had a CoE that listed the Lamai and the Renaissance. We also both had SHA+ certs for the Lamai, a 3 night stay at the Conrad, and an overlapping 7 night stay at the Renaissance. We figured as long as we had the CoE's in hand, we could work it out there.

Stays
The stay at the Lamai Samui (previously Le Meridian) was great and the staff were super friendly. I think there were 4-5 rooms occupied the entire time but we rarely ever saw the other guests. After some communication between all of the hotels, we were able to lock down that we would spend one night at the Conrad and then rotate to the Renaissance after that. The Conrad was super helpful in contacting the Samui+ "Command Center" to make sure everything was alright and we wouldn't get in trouble based on what our CoE's happened to say. We stayed on site at the Conrad due to booking an FHR rate and having a ton of FB/Spa credit to use during our one day. After that we transferred up to the Renaissance and started doing a bit more touring. We weren't specifically researching SHA+ closed route tours, but were able to do everything that we booked with pickups from the hotel. One was an island safari tour around Koh Samui and another was a longtail boat tour to Koh Mudsum and then some snorkeling. Both were private, so no input on doing shared tours during this second week.

Overall
I really appreciate that Thailand is being careful with their re-opening. There are certainly some aspects that feel like it's a bit of overkill safety, but everybody will have their own opinions about that and I appreciate that they are at least erring on the side of caution. That being said, once you are walking along the beach, you obviously have the freedom to basically do whatever you want and as far as scooter rentals, restaurants, etc go, nobody asks you how long you have been on the island before renting or eating. Do with that information what you will.

If anybody has any questions, I can try to answer based on my experience.