That sounds fine. I think. I'd be tempted to bump up the numbers of the rasporas. I have 12 penguin tetras as the main school in my 54 gallon tank and that fits well enough but I think 14 schooling fish in a 180 isn't that much and they're always happier and prettier in bigger groups.
I'd also probably stock really slowly, start off with the hardier fish and get the hang of plants and the tank before adding the more delicate rams and discus.
I used to have sterbai cories, they're pretty much my favourite cory. Started out with 6 but they spawned and I raised the fry so I had a few extra later on.
As for the lower/middle/upper sections of the tank, the fish will do just what they want. If you have plants that reach the surface the fish will feel safer to venture higher up more often, but even then individual fish will sometimes decide to not swim much in the level they're "supposed" to be in. Like I had a gourami that usually stayed in the lower to middle level of the tank for some reason.
Also do read up on discus and discus in planted tanks, lots. I think there were some nice threads in this forum on the topic. You need to make sure that everything you do in terms of other fish etc. is geared towards the discus for when they go in.