tl;dr: My world has airships using vacuum spheres made out of a super-strong and lightweight material. I'd like to know how versatile such airships could be used, and how big the spheres would be compared to the rest of the ship.
Background & maths:
I'm building a steampunk/magipunk fantasy world that involves lots of flying islands which, naturally, means you need some kind of flight to get around. Additionally, this world features a magical material that is simultaneously both very strong and lightweight (among other unique properties).
It's visually more similar to glass than metal, but for the purpose of this question, let's call it Beskar, because just like the Mandalorian currently carries the Star Wars franchise, I intend for this material to be used to carry airships via buoyancy.
Functionally, this would work via the creation of vacuum-"filled" spheres with a Beskar hull. I haven't decided on an exact density or strength for Beskar yet, thus those are still flexible. However, assume the strength to be sufficient; it should take Hulk levels of strength to break a 1-cm-pole made of Beskar. I don't generally like handwaving stuff or soft magic systems, but I want a super-strong material, so this is going to be as strong as it needs to be.
For a first approximation, assuming a sphere with a radius of 5 meters, we can calculate a volume of roughly 523.6m³. According to some buoyancy calculator I found on the web and assuming an air density of 1.225kg/m³, the mass of the displaced volume (and thus the weight it can carry) equals roughly 640kg.
Assuming that the Beskar hull would be 0.5cm thick (i.e. a hollow sphere with a 5.01m radius), this means we have roughly 525.2m³ minus 523.6m³, or roughly 1.6m³ Beskar. Because the contraption should be actually able to float, I'll declare Beskar to have a density of about 140kg/m³. I'm aware this is lighter than any solid material in the real world (even some aerogels weigh more if my google search is accurate), but what's the point of magic if everything is exactly like in the real world?
(Quick scaling maths: 10m sphere: 6.3m³ or 880kg of Beskar, lifting capacity 5.1 tons. This is a lifting efficiency of 83% as opposed to 72% with the 5m sphere. 20m sphere: 25m³ or 3.5 tons of Beskar, lifting capacity 41 tons, 92% efficiency. These calculations assume the same hull thickness of 0.5cm)
Unlike the basic maths above, what I'm actually interested in and can't judge myself is how practical an airship like this would be. Mainly because I don't know anything about ships and their construction. Zeppelins in the real world are gigantic balloons with a comparatively tiny cabin, which is impractical and not what I want (there's a reason Zeppelins are generally not around anymore, except as tourist attractions).
Thus, how viable would an airship with this technology be? Would it just be a little better than a Zeppelin, could it be used as a decent transportation vehicle without being 98% balloon, or would it even be viable as a cargo ship or a military vessel with thick armor plating? And roughly how big would the spheres be compared to the rest of the ship?
Side note, as it's probably relevant: Beskar is obtainable only for significant sums of money, as - while it's far from rare - it is supremely difficult to harvest and process. Thus, I could design such ships to have a supporting skeleton made of Beskar if functionally necessary or the buyer is Beff Jezos, but the floor, walls, etc. would likely be wood or metal. If possible, I'm interested in the viability both with and without a Beskar skeleton.