pre-pandemic I was a big user of the Accor lines, all of them from top to bottom.
Sofitel is pretty close to the top so you usually have a pretty good idea of what you will get. In France/Monaco, I've stayed over the years at Sofitels in Aix-en-Provence, Lille and Reims, and probably others. Many others in England, Germany, Italy.
Figure a step up from Novotel and just a tiny notch below M. Top end business class, with expensive rates and food to match.
The fanciest was in Rome, on the Via Veneto, and at Baden-Baden, and in Frankfurt. The plainest was in Lille (that was just before it was downgraded to a Mercure).
If I weren't paying for them I'd stay at most of them again - but I am paying so I tone it down a bit now.