There’s an interesting caveat, looking at recent war history …..

War technology has always been a “battle” between offensive technology and defensive. However in recent years, offensive dominates. We may have reached the limits of physical materials such that there is no defense. Certainly a lot of todays fighting requires stopping the attack or making it miss, rather than trying to survive it.

There’s no reason to expect that shields can exist, so it’s quite possible we can hurt the aliens and their advantages are standoff and intelligent weapons, reconnaissance, targeting. Looking at recent wars, would we be like Iraq, appearing similar in destructive ability but overwhelmed, or more like Ukraine, appearing to have no chance but successfully fighting back? Ukraine’s advantage is partly economic: using cheap drones to destroy expensive or nonreplaceable tech. Imagine the Aliens as Russia, with all the apparent advantages in size, tech, experience ….. but they only have the weapons they came with and we can at least sting them, we can make them spend irreplaceable weapons on our much cheaper technology

Or think of Stargate SG-1. Humans technology was primitive, but the weapons could still kill. A combination of unwieldy political structure of the aliens and clever application of force managed to minimize the impact of the technology advantages. Then of course making the right friends enabled those humans to leapfrog ahead

To cross the width of space, their technology must be far ahead of ours. Imagine a modern army fighting one from the 18th century, and you could imagine what a tank, a machinegun, modern artillery or whatever other aspects would do. BUT: There is also the point that we would fight locally, while they would need quite long-winded logistics.

In regards to the long winded logostics (I read this from a second hand account and I'm sure this idea is from some scifi book) -a really fun idea is that if the aliens would send a war fleet our way and it takes say 50 years to get here... it is reasonable to assume that in those 50 years the aliens will do some technological breakthrough in both drive and weapon departments that by the time the fleet would get here a more advanced fleet would already be fighting the war - possibly even already won.