My figures could be corrected, by the way. They are just impressions. If you have something more exact, please feel free...
But imagine waging war on an enemy 120,000 to 150,000 miles away... The tech level is at least 100 years behind what we take for granted in our own timeline in first world countries. For Sharona this means trains and laying track. For Arcana we are talking about transport dragons and sliders.... Logistics would have to be a nightmare.
What this has to mean would be that resourses for such things as food and fuel will have to be developed in secure areas closer to the front. Raising crops would be part of that. Mining coal and drilling for oil. You might even need foundries and assembly plants.
If I'm right about this, the war effort for Sharona is going to have to include a huge infrastructure off Sharona in those universes close enough to make the logistics practical. With Arcana's magic, I'm a bit less certain. But there are obvious limits to everything including magic and transport dragons. So I would suspect that Arcana will also need to develop resourses closer to the front to sustain the armies it will need for the war.
So how does this impact the storyline? Will the war be fought in the universes between Arcana and Sharona? Will anybody actually break into the other side's home universe or are both sides simply too far apart for that to be a practical expectation...

Don