Without being sure of what those windows are from, it might be worth considering creating a flat roof/ deck on that single garage and replacing the first window with a sliding door to access it. Continue he same balustrade as your fence with have and create a terrace. Slatted balustrade might provide the privacy in screening, and a nice place to stand out at evenings. I think a colourbond roof would modernize this home in the right way, it's low pitch is suited to doing so. As for the windows, I personally like timber awning windows for this style home. Although I think a louvre window would look amazing where that long narrow window is, and if it happens to be within your stairwell, it would create a fantastic breezeway and vacuum the hot air upwards and outwards. The main structure of your garage, I would create post and beams that jut out over the entrance path not a covered roof, just the beams, which would be the joists from the garage roof/ deck. This would tie into the architecture and soften the boxiness of the exterior facade. Also it will direct you through an interesting entrance and lighting and landscape details could really wow you.

How about a more contemporary wire rail system as shown below. Also a lovely green grey upstairs may work. The one below is Taubman's battle green full strength - computer colour of it is not accurate.

Seriously looks like a brand new house, I am thoroughly impressed, a lot of work and love must have gone into this.

If you are worried about invasive roots you might want to get rid of the magnolia in your front lawn. These little gem magnolia's might be dwarves for their genus but their genus is a massive tree way too large for a suburban yard at maturity. A lot of people don't realise how large they will get because they are slow growing. The tropical garden look is all about large sized leaves and vivid colour. So a mix of coloured leaf plants and greenery with over sized leaves works best. A rhapis palm is a good screening palm as well as having architectural appeal since it's globular in shape. Looks best in a feature pot and one each side of your portico would look great. For hedging I can't urge you NOT to use bamboo enough. I purchased a house where a bamboo has been hedged on 2 sides. I hate it for these reasons. The particular variety I have cannot be clipped to keep it at a specific height. The entire thing keeps growing skyward until it set seeds and then dies back. Giving me a hedge that looks okay for around 6 months of the year and looks like dead grass for the other 6 months. Clumping bamboos are NOT non invasive. They will take over your yard. They just do it by the clumps getting larger over time and spreading outwards in concentric fashion instead of sending out runners linearly. They are high maintenance if you want them to look lush. You have to get into the clump and constantly cut out the dying culms otherwise you get a yellowed and dead looking section in your hedge. They are extremely messy constantly dropping leaves. I've tried mulching the continual fall but the leaves actually clog a mulcher and can't be recycled easily. Getting rid of a clump is nigh on impossible once established. I tried digging one of mine out. The rhizomes are like concrete and cannot be easily broken up with any kind of tool. I would need to hire a bobcat and dig them out to get rid of them. They have to actually be tied up into clumps with string, otherwise they fall over and look like weeds. The rhapis palm above is very bamboo like but unlike bamboo it isn't a grass so it will grow perennially without the massive die off of bamboo for many years to come. Most people don't realise that because bamboo is a grass it's lifecycle is very short. Each culm will live only 1-2yrs then die. The clump renews itself by sending up new shoots which results in an ever increasing clump size and a lot of dead poles in the clump. Bamboo is wonderful stuff in a plantation where the culms are continually harvested and clumps thinned out. They are a massive amount of work in a garden though.