First off, welcome to cruising! We've been sailing since 2006 and are sailing Scarlet Lady in July. It will be our 16th cruise and 8th cruise line because we like to explore and see what everyone has to offer.
We booked Scarlet Lady primarily because of the food experience. It does sound like the ship is a very quiet, chill place during the day which is fine by us, but what we will be missing is an indoor solarium style pool. That is our favorite place to chill on any cruise ship during the day. But of course we knew that going in to the booking. We have a Cheeky Corner Suite so we will have plenty of room to chill on our balcony or in Richard's Rooftop.
Another line line you may consider is Celebrity. The Edge Class does have solo cabins and they are considered a 'luxury line' that now includes a drinks package and WiFi with all bookings. You will still need to pay for the specialty dining, but the main dining room and a few other spots will be included, but the cocktails, soft drinks and WiFi will be included. We've sailed Celebrity four times and it's a nice blend of super chill during the day, but with a lot of scheduled activities if you want to do stuff. And a full slate of entertainment in the evenings. They also have some of the best bars at sea if you enjoy your cocktails. While not 'adults-only' Celebrity does skew more adults because there are no major 'kid-friendly outdoor activities like the Royal ships, so you find far fewer children on board those ships.
They're probably the closest to what Virgin has to offer in terms of the other 'mainstream' cruise lines if you want to compare. Again, welcome to the cruise family!