Gioenne - yes, that's what we were thinking for the timber option. Maybe slightly narrower slats. Do you think it would look too modern? As for budget, $2000 maybe? Hadn't considered the concerte height/thing. Now you mention it, would love to change all the concrete but I know aggregate is expensive. Not a big fan of laser cut or vertical slats. The first I feel is too modern. The later, a bit dated! I'm usually really good with design decisions but this is doing my head in a bit!

Humblehouse, it would be good to see where the gates or panels are going. Are they for screening or just decorative?

You could also consider laser cut aluminium screens which are powder coated in a Corten look finish. We used them in our new house. Screens by Decopanel in Brisbane. We have a real letterbox made of real corten, but were worried about rust staining our floors so used the aluminium for the breezeway screens. Photos below

I would go with the same style railing as the front of the house. Place the fence across (with a gate in it) after the second pillar, between the exterior light and the window if you can. You might need to make a larger "platform" with perhaps decking, to accommodate fence swing. If you use decking it might look nicer if you drop a step from the tiles. Possibly could extend your tiles along a bit and have gate sit on the tiles. Your existing wooden steps could then be put in or, do a couple of steps again, more of a platform, then more steps so you are spreading the distance down towards your back yard. If you hinge the gate behind the pillar that may look nicer and swing away from house towards the side fence and not to get in the way of the window (if window is an issue possibly a sliding gate?).