@ScarboroughFairy I hope your day so far has been good and you are travelling safely or have decided not to go after all.
I'm very familiar with the A9 (which I'm sure is the road you mean). You are correct that there are often crashes on it, I always allow extra time for this reason. The crashes are almost always caused by an impatient driver dangerously overtaking. Even if there is no crash on a particular day, you will see these idiots overtaking, it is breathtaking how big the risks are that they take.
However, the road itself is fine. There has been a lot of work done in recent years to have more and longer stretches of dual lanes. If you do choose to drive it at some point, doing 40 rather than 60 will not help you at all, most of it is perfectly fine to do at 60, depending on conditions.
If you do drive, any alternative route will take at least twice as long and those roads will be very windy, it definitely won't be any safer.
That said, I am a very confident and in my opinion capable driver, and I avoid driving in Edinburgh if at all possible. The outskirts are fine, but I find the centre and even around Leith very difficult to navigate despite having lived in Edinburgh for years. It's all weird one way systems and tight turns, and if you go wrong it takes ages to correct. Parking is hugely expensive too. So if possible, take the train.