Full view mode is just a shortcut to the 18.5:9 mode in the picture settings. It's useful sometimes but do note that the resolution drops quite a bit as the sensor crops in top and bottom to get the wide aspect ratio. You actually get more in a shot using the max resolution, you can then crop to 18.5:9 or other later on in any image viewer.
Full View just looks cooler when in use really.
Solid Explorer works on Oreo beta, just the SD card write permissions doesn't work, so for the time being I have it still installed, but am using Amaze File Manager instead which is actually really really good. Supports the same features as Solid, but with a much more simplified UI, and the built in sftp server is amazing, allows you to send and receive stuff via Windows by simply ftp://IPORT from any Explorer window.
Also I am finding that SMB transfer speeds via Amaze is in orders of magnitude faster than Solid and other file managers that support SMB.
That's Android 8's new "feature". Simply hide it using this app: https://play.google.com/store/apps/details?id=com.iboalali.sysnotifsnooze
Odd. Just for this month or from now on?got my S8+ on EE contract - just woke up to find they have increased my data allowance from 10gb to 15gb for free - ?!