Reactor goes between the two engines, hypothetically there would be space for one on each side but as mentioned it doesn't need a lot of raw throughtly power, it basically needs little more than what is needed to move and run the radars and other support systems, it's weapons are mainly anti-fighter, it's anti-capital weapons exsist and it might be able to tank damage well enough to take out a destroyer, but if it gets into that sort of fight it's lost allready because that means it's escort of 1-3 Orion destroyers, 3-6 Grendel dreadnoughts, and dozen or so Freki/Finris/Leviathan cruisers have been destroyed. It's mainly a giant support ship, supplying repair and fabrication services as well as long range radar and comunications support. And of course being a hell gate spewing forth an absurd number of fighters, which is where its real offinsive power lays. The number of fighter and bombers it houses and supplies makes it a regional power unto it's self and often a command ship.
It's nearly as wide as an orion is long, though it probably would be 1.5X the mass, lot of empty space, including internal. The main bay is large enough to acomidate/repair small cruisers, and iirc this might be the only ship big enough to deploy Vanir strategic bombers. Sol only has a hand full of these and each one represents a huge chunk of their fleet.