Glad to see you've settled on a few places already. You're already so far ahead of the game! We visited for nine days (plus 2 to travel) in May of this year, and while we wished we could have stayed longer, I think you will find if you plan well ten days should give you plenty of time to get a nice taste of Scotland. (For example, we wanted to see the Orkneys, but realized it would have severely limited our time elsewhere, so we added it to our plans for next time!) You may have a different travel style of course, but ours is more that we like to keep on the move, and most of the time we stayed only one night in each area. (Several times we stayed for two nights). Main point is, we never felt rushed. And I would highly recommend renting a car. It gave us so much freedom!
Everyone has different goals for their trip, and you certainly don't have to do what we did, but here's what we managed to see in our nine days:
Day 1: 1/2 day touring Edinburgh; we arrived from Heathrow around 10 am and once we got out of the airport, spent the rest of the day touring around the city
Day 2: more Edinburgh, including castle and an evening Cadies/Witchery Tour
Day 3: picked up a rental car (I would like to suggest Arnold Clark, using Celtic Legend online; awesome service! I can give you more info if you'd like) and drove to St. Andrews; toured there, then drove to Pitlochry for supper and to spend the night
Day 4: drove first to the Highland Folk Museum in Newtonmore (Outlander tv series, Season 1 Episode 5 filmed here; I too am a fan); leave extra time to stop and view scenery along the way - it's spectacular; drove next to just south of Inverness (Daviot), dropped luggage at b&b and toured Culloden Battlefield and Clava Cairns
Day 5: visited Urquhart Castle in morning and Cawdor Castle in afternoon; stayed again overnight in Daviot, same b&b
Day 6: drove to Skye (b&b 10 min. outside of Portree) via bridge; along the way we stopped many times to enjoy the scenery, stopped at Eilean Donan Castle to take pix and small snack break; ate late lunch in Portree; checked into b&b; visited Neist Point Light
Day 7: drove Trotternish Peninsula, including 2-hour hike of Old Man of Storr, and stops to see Lealt Falls, Kilt Rock, Flora McDonald gravesite, as well as lots of stops for photos
Day 8: left b&b; stopped for a bit at Sligachan Bridge; left Skye by bridge; stopped for several hours in Glenfinnan, touring and watching Harry Potter train go by; several hours driving down to Glen Etive (BEST PART of the whole trip!); and finally on to Arrochar for the night
Day 9: toured Doune and Stirling Castles; hotel tonight about 10 minutes from airport
Day 10: leisurely breakfast, drop off rental car just outside airport, 1:50 pm flight to Heathrow, then on to home (Philadelphia)
I'm in the process of posting my trip report now
so feel free to follow along if you'd like. I hope to have it done in the next few days or so. (But warning, it's long with lots of details!)
Let me know if you have any other questions I might be able to answer.