Different things seem to work for different people, but I think a lot of it is dependent upon the personalities of the individual chickens. Chickens are social animals that are able to get along together due to the pecking order. That tells them who gets to eat first, get the best roosting spot, or get any other perk without a lot of squabbling. Packs of wolves and herds of cattle are much the same way. They have to learn their place in the scheme of things. The pecking order is critical to the survival of a wild flock, herd, or pack and can get pretty complicated. Your chickens are not wild but the instincts are still there.
My set-up is different from yours and I'm sure my goals are different. I generally let them fight it out as long as no blood is drawn. I'm not sure that is your preferred solution. There are tricks you can use to ease the integration process.
House them side by side for a week or so where they can see each other but not physically get to each other. Throw food down where they eat side by side but are separated by the wire.
When you integrate them, make it on the weaker chicken's home turf. That seems to confuse the aggressors and they spend energy exploring their new surroundings that they might use to defend their home turf.
Have separate feeders and waterers for a few days. Chickens can be possessive about their feeders and waterers.
Some people recommend putting them in the same coop at night so they wake up together. I don't know if this helps or not. They still have to establish a pecking order. Sometimes it seems to go smoothly and sometimes there are disasters. I think that sometimes the pecking order is worked out before the humans know anything about it, so it seems to work. But it is possible it helps. I really don't know.
Giving them lots of room like you are doing is helpful. It gives the weaker a chance to get away or hide. As you have noticed, there is a personal boundary that the Austalorp will enforce.
And do as you are doing. Let them work on the pecking order without letting it get too serious. Let them do a little pecking but then break it up before it escalates, whether that is with a water hose, a broom, or just walking over and crowding them. Whatever works for you.
This is a long way of saying, I think you are doing fine.