all i got for ya is that Hyo Sho is probably from 氷晶 which means “ice crystals”. i’d start googling ice domes and dome cities to get your basic feel for them. you could go in any direction, really. are they large neo-material domes set above cities to contain atmosphere and warmth? geodesic manipulations of ice to form futuristic igloos? small metal and glass domes to allow sunlight and airborne access to largely underground cities? you can also use Thaton and the Martian cities as your templates, as they are the other Yu Jing settlements with dome cities, or the Lunar colonies more vaguely.
in terms of size, Svalarheima is home to 400M people, which is roughly 2x the pop of Russia, Canada, Sweden, Norway, Denmark, Finland, Iceland, and the smaller islands of Scandinavia. so i would benchmark a city’s population based on what you think might be an analog–are you thinking of a city like Stockholm where 20% of a region’s population might be housed along with the administrative, political, and economic importance, or something more like a Utqiaġvik or Hammerfest tied to industry, or even a Nagurskoye or Alert military/research style settlement?
in terms of features, i would scale them to whatever size city you’re thinking of–were they connected to nessium extraction sites, situated in areas of natural phenomenon and geographical importance, or just bare bones heaters and one story buildings underneath a modest dome?
fwiw, it’s weird that the YJ book only writes about Svalarheima in relation to the Japanese. you’d think it would have more since it ended up being such a big focus in the N4 launch, though maybe the CB writers were withholding as they fleshed out the lore for the new edition.