Re; Elysium, my bet is that it's a slightly enlarged variant of the Quarter. Quarter stands about 300m tall, which as has been noted is around the height of a 90-story building. I can buy that from the screenshots provided and can dismiss the rest as cosmetic differences. If anything, consider it the same sort of differences between the Nimitz-class aircraft carriers and the forthcoming Gerald R. Ford class. The latter is a teeny big bigger and the tower is completely different in configuration and placement, but otherwise they share the same basic shape.
And regarding that city dome in the lake, note that while it's definitely not the scale as Island One, it seems to be much smaller than City 7 as well. It's got skyscrapers poking through the dome and all, but compared to the Manhattan-esque metropolis skyline that comprised most of City 7, and what was basically the entire City of San Francisco in Island 1, this one seems to be a much smaller city with some Zentradi-scale trees around it. Maybe half the size of City 7? Round about what the ol' Megaroad class would be hauling inside? Something that Elysium could dock with? We don't even know how long Barette City here has been in existence. Could be a relatively new construction, or it could be decades old - it's impossible to really tell given how fast construction happens in the Macross universe. The locals, assuming they invited / allowed the colony to settle there, have certainly wasted no time integrating the culture. That Chaos is using Ragna as a base of operations for its state of the art planes and tech is indicative that this is no backwater planet.
Tech-wise, this is a delicious world-building episode and I'm loving it. Mark