Whatever you do never plant a gum! They have no place in suburban areas! The sooner the council realises that these trees kill people the better! We have had two gum trees fall on the back of our house now, one in 2012 and one in 2014. We are so lucky that myself, my husband, three children, three dogs, five Guinea pigs, two parrots and one bearded dragon were not injured. It's just a miracle not once but twice! I still don't know how we escaped unharmed. The gums do not have a stable root system and they grow very shallow, they get to the point where they just fall over. And the scary thing is they fall silently. They are not called 'Widow Makers' in the bush for no reason. I like the Tuckeroo tree, not sure of scientific name. They grow with a straight trunk and keep their foliage in a straight and symmetrical line along the bottom and grow hiding their branches. Essentially they look like a large mushroom. They are green all year too. I think they get to about 6 metre or ten if they have to reach for the sun.

Add a couple of outdoor mirrors in strategic spots on the fence. Plant things in front of them to suggest additional depth to your garden. If you are worried about the fence, prop them on something low and lean them against the fence with a garden in front. I'd possibly look at painting the fence a dark colour and plant light green or coloured plants in front. I have a beautiful one that has pink leaves that glows in the sunlight. Add a mirror and you could create a beautiful space.

I am no expert but I think you are quite right. Any growth below the graft needs to be removed.

Pittosporum is very quick growing and has a narrow trunk and thin branches so its probably the best option if you want a tall and dense, but also thin hedge - I have Silver Sheen as a hedge in several areas in my yard and it grew from 1 foot high to over 2m in 2 years. Alternatively clumping bamboo (not as invasive but probably best planted in long containers and placed along the fence line) will quickly give you privacy and both the leaves and trunks of bamboo are attractive. If you go for one of the Lilly Pilly hedges Id recommend one that doesnt fruit as much, as the berries can make a big mess especially when the birds notice them.