Second screen is new??
"briefly shown at Unpacked, is the ability to use the forthcoming Galaxy Tab S7 as a second screen for a Windows 10 PC."
Funny that - I'm currently doing exactly that, using spaceDesk, on a Sony tablet (Xperia Z4 and have used it on my Z5C phone too).
Its a bit slow over wi-fi, but perfectly usable when USB-Tethered.
Hate it when large manufacturers try to sell something already around as 'theirs' or 'new'.