Bear in mind if it's scenery you want now is the wrong time of year. At present sunset in the Highlands is about 730pm and sunrise about 7 am (Aberdeen times about 15 minutes earler than Fort Wiilliam, Inverness somewhere in between) That means you will see no secenery southbound as all departures are after sunset. Northbound the sun will rise as you reach Loch Lomond, Dalwhinnie or Aberdeen, but the time of sunrise chages rapidly at this time of year and by December sunrise isn't until 9am so you won't see much at all except the run along the edge of the Monessie Gorge in Glen Spean, betweeen Tulloch and Roy Bridge.
Wait until June and sunset isn't until after 10pm, by which time the southbound portions will be crossing the Tay Bridge, or at or Dalwhinnie, or Loch Lomond, and it will still be twilight as you cross the Forth Bridge, or reach Perth or the Firth of Clyde
And northbound it will be rising before you even leave Edinburgh