There a tons of great routes, often people talk of the Highlands but there are great roads all over.
I've been lucky enough to spend a few years driving all over the country. I've been right out into the arse end of nowhere, drove to the end of many single track roads, places I'd never have went of my own volition and pretty much all of them have been great.
The west coast gets good press but for example some of the best roads are in rural Aberdeenshire, my advice don't discount anything. Even the A9 which does have some cameras (the most northerly being at Blair Atholl iirc) is a good drive and it's the quickest way to get to the Highlands if that is what you are after.
I started putting a route together on Google Maps, it's 1100miles and there's a lot more I'd like to add
Whichever route you pick I'm sure you'll love it! If you plan to do it in the summer then be warned the A9 and A82 will be busy. These two roads are the tourist highway and will be full of coaches, caravans, trucks and car club convoys.