Futuristic Hippie Communes
The latest Isaac Arthur video posted on his YouTube channel today is titled "Arcology Design". Basically sort of like his ecumenopolis video but it's more apartment building than city and not planetwide.
I tried to do some more research about the arcology concept on the internet after watching the video. I still don't know if there is a minimum population. It seems a home can be designed to be an arcology for a large family. Is the TARDIS from Doctor Who an example of an arcology or do types of spacecraft not count? I am not sure. I am sure the "Paradise Towers" episode from classic Doctor Who was set in an arcology.
Since an arcology is basically a more eco-friendly skyscraper it seems most of the details from the "Skyscraper design and construction" entry from Wikipedia apply. The building's form could be drastically different from one found on Earth if it's built on a low-gravity planet.