If Dundee is murky then Perth is either going to be at least as bad, or sparkly clear! If it is the haar at Dundee then Perth is often clear. If it is low cloud and assorted weather then Perth is likely to be worst being higher and nearer the hills. Coming from the south, Fife has some surprisingly high bits.
Transiting Edinburgh south to north can be long winded it is usually much quicker to either go low to the west or higher to the east over the water. Either way they are usually very keen to talk to passing traffic to ensure transponded levels are correct.
Fishbang and his crew will usually co-ordinate all this long before you arrive if you are talking to them.