You won’t have too much trouble finding accommodation in Edinburgh but my advice would be to book it as soon as you can, or it will be proper expensive. We have loads of chain hotels, b&bs, and services apartments (Fountain Court are a good one). Don’t air BnB a flat that’s obviously a full time rental, it’s ruining the city. Happy to answer any specific questions about places to stay etc
If you’re going north there are plenty of trains to great places, and they’re generally pretty reasonably priced. Pitlochry, Oban, Arrochar are all a short trip from the central belt and lovely to visit. Oban has ferries to some of the islands. If you’re feeling really adventurous, you can go from Edinburgh to Inverness (4 hrs) or all the way to Thurso in the far north in about eight hours.
The drive from Lomond to Skye is sublime, it just keeps getting better and better as you go. I’d heartily recommend Skye, loads to do there and it’s beautiful every way you look. It might be my favourite place in Europe.
Did a driving and walking holiday from Glasgow > Kinlochleven > Skye > Harris & Lewis > Ullapool > Inverness in Autumn and it was the best. Ullapool worked as a good base (+ it was beautiful and has great food/drink) for driving some of the North Coast 500 as previously mentioned, and the islands blew my mind. Didn’t want to leave anywhere and felt like my itinerary barely scratched the surface, definitely plan to try to see loads more of it this year.
I’ve been up to Assynt a couple of times, it’s completely wonderful - there’s absolutely no one else there. We stayed in Inverkirkaig near Lochinver, which is north of Ullapool and at the end of something called the Wee Mad Road, which sounds like something from Father Ted but is real and aptly named.
Best thing we did was finding the tiny beach of Port Alltan na Bradhan. We had it all to ourselves all afternoon until a minke whale showed up, which was pretty amazing.