Those changes would make any car look sportier, so designers are toning it down in other areas, especially character lines. The bits we can see now include the headlights and part of the rear lights, both evolutionary versions of what we've seen on the 3rd generation CLS-Class. By that, we mean they are more tapered and longer, but Mercedes is even trying to throw us off with CLS taillight stickers.
The prototype is back to wearing covers over its door handles, but we know they are another major source of change. Mercedes opted for a fush-fitting setup, a bit like what we see on some Jaguar and Range Rover models, but also Tesla.
Inside, the parallel between the S-Class and American-made EVs continues with a screen-heavy setup. You can't see it in this video, but previous spyshots showed a large tablet cascading down the dashboard and console, with another more familiar screen in front of the driver. No other Mercedes model has this setup right now, and that will continue at least until the W206 C-Class comes out, if not later, which will cement the flagship status of the S-Class.
A lot is riding on this car, but just in case it doesn't work, Mercedes is also working on an electric flagship. The EQS should come out at roughly the same time, cost about the same, but feature much cooler styling.