Since most of my driving is on Highland roads I can't say that the major routes are any different from other parts of the country. Road surfaces do vary though without any logical reason as far as I can tell.
Off the main roads the condition of the surface varies considerably and maintenance of these leaves much to be desired due to budgetary restrictions. The underlying surface on these roads is often not great as they are constructed on top of old cart tracks and despite being 'tarmaced' the surfaces shift and deteriorate quickly.
Often a repair on these roads is just a cold tar approach, where cold tar (or lukewarm) is sprayed on the surface and then gravel is sprinkled over. It's then left for cars to bed this in. In doesn't last long. The following winter will see the surfaces erroded once again.
Pot holes are numerous and I'm convinced I've heard dwarf voices coming out singing the 'Hi Ho...' song
Most of the money gets spent in cities and on the main interconnecting routes.
Personally and for just On-road driving I've never bothered about 'special' tires and have driven in extremes of weather conditions. Again, IMO, its just a case of adapting your driving style to the conditions.