My wife had an aunt who emigrated to the US and lived in San Francisco. The routes we took getting there varied pretty well every time. There was a sort of pattern - north from London, just south of Iceland, cross southern Greenland, north of Hudsons Bay cross into the USA somewhere between Winnipeg and Calgary, down to Point Reyes, cross San Francisco city at about 10-12000 feet, down the Peninsular, then reverse course to land up the Bay over the San Mateo bridge to the 28 runways.
A couple stand out. On one occasion we went as far west as Seattle then down the coast and back in September this year we crossed into the USA over the Idaho panhandle down to Point Reyes and then landed on 19R which is almost unheard of according to a BA 747 pilot of my acquaintance.
Coming back has could involve being either north or south of the Great Lakes, I've ended up entering UK airspace over Lands End, Shannon and Southern Scotland. This year coming home our initial cruise was 33000 (I think), then 35000 and finally 39000 - that kind of vertical profile is often related to the weight of the aircraft and as it burns fuel and gets lighter it's able to climb higher. It can also be a way of improving the effect of wind, it's surprising how wind can vary with altitude. In our case I suspect it was a combination of factors with the ability to climb being weight restricted to start with and then as fuel was burned we went higher to take advantage of winds because although the flight from London had arrived 40 minutes late and we took off late as a result we actually arrived in London on time - we got the benefit of the winds that delayed the outbound.
Planning long haul flying is about a balance. That 747 pilot I know also flew 767s long haul for a while. With twins it's not just about fitting in with the weather and great circle (and North Atlantic tracks). There are rules about access to diversionary airfields that need to be taken into account - they have to be predicted to be open as the aircraft passes.
Even short haul has variations. The usual route Paris to London is pretty obvious but on one occasion we headed west then up to Le Havre, Southampton, Heathrow. Geneva usually involved going down to Lyons and turning left but I've also gone over Belgium and Germany.