Autoblog's most recent Luggage Test features the Integra.
www.autoblog.com
It is a gigantic mesh piece bracketed my rigid plastic. This means that you're pretty much screwed if you suddenly need space beyond what's below the cover. You ain't storing this thing inside the car. There is a slight silver lining, however, which I'll get to momentarily.
First, let's see how many bags fit with the cover in place (ish). As in every luggage test I do, I use two midsize roller suitcases that would need to be checked in at the airport (26 inches long, 16 wide, 11 deep), two roll-aboard suitcases that just barely fit in the overhead (24L x 15W x 10D), and one smaller roll-aboard that fits easily (23L x 15W x 10D). I also include my wife's fancy overnight bag just to spruce things up a bit (21L x 12W x 12D).
That's all the big bags up there, but as you can see (above right), the blue bag is totally smashed. I couldn't do that if there was actually something in the bag. Ergo, forget this.
This would be the four biggest bags plus the fancy bag, which is still a bit squished but usable. There is still an issue, though.
The black bag at the upper right forced the cargo cover up and out of its bracket when the trunk lid was closed. The trunk still closed, though. The cargo cover also didn't break and still covered what was below, while the bag itself wasn't squished.
I'm calling this totally acceptable.
OK, now let's remove the cargo cover.
Removing the cargo cover does allow for the small blue bag to fit atop, and therefore all the bags of the luggage test (OK, so minus 10% of the fancy bag).
Sure, the bags are getting roasted in the sun under a greenhouse, but hey, they fit.
So, how does this compare to the Civic???
All the bags fit in the Civic sedan trunk, no squishing whatsoever, no difficulty and with some space left over on the other side.
Basically, the area between the wheels is wider in the Civic and the entire space is longer.
fit the bag on the right, nor enough length to completely fit the small blue bag at the front.
Basically, those extra 10 cubes for the Integra are entirely up near the rear head restraints and close to the roof (I guess). That's not terribly useful space. Also, since I mentioned it from the get-go, small SUVs like the Crosstrek and CX-30 could stuff in all the bags more easily without squishing and with more room to spare. They do block your view out the back in a way the Integra doesn't, so with some caveats, it's not entirely a silly comparison to say the Integra has comparable trunk space to a small SUV. It's just that the Civic has a more usable trunk than them all.
All of that said, however, should you compare the Integra to an Audi A3 or Mercedes CLA, it will absolutely swallow them whole. Both have traditional trunks in the 10-11 cubic-foot range. They're quite small. The Integra's trunk is not.

Acura Integra Luggage Test: How big is the trunk? - Autoblog
The Integra cargo capacity is 24.3 cubic-feet, but that amount inflates how much usable space it really has.

It is a gigantic mesh piece bracketed my rigid plastic. This means that you're pretty much screwed if you suddenly need space beyond what's below the cover. You ain't storing this thing inside the car. There is a slight silver lining, however, which I'll get to momentarily.
First, let's see how many bags fit with the cover in place (ish). As in every luggage test I do, I use two midsize roller suitcases that would need to be checked in at the airport (26 inches long, 16 wide, 11 deep), two roll-aboard suitcases that just barely fit in the overhead (24L x 15W x 10D), and one smaller roll-aboard that fits easily (23L x 15W x 10D). I also include my wife's fancy overnight bag just to spruce things up a bit (21L x 12W x 12D).
That's all the big bags up there, but as you can see (above right), the blue bag is totally smashed. I couldn't do that if there was actually something in the bag. Ergo, forget this.
This would be the four biggest bags plus the fancy bag, which is still a bit squished but usable. There is still an issue, though.
The black bag at the upper right forced the cargo cover up and out of its bracket when the trunk lid was closed. The trunk still closed, though. The cargo cover also didn't break and still covered what was below, while the bag itself wasn't squished.
I'm calling this totally acceptable.
OK, now let's remove the cargo cover.
Removing the cargo cover does allow for the small blue bag to fit atop, and therefore all the bags of the luggage test (OK, so minus 10% of the fancy bag).
Sure, the bags are getting roasted in the sun under a greenhouse, but hey, they fit.
So, how does this compare to the Civic???
All the bags fit in the Civic sedan trunk, no squishing whatsoever, no difficulty and with some space left over on the other side.
Basically, the area between the wheels is wider in the Civic and the entire space is longer.
fit the bag on the right, nor enough length to completely fit the small blue bag at the front.
Basically, those extra 10 cubes for the Integra are entirely up near the rear head restraints and close to the roof (I guess). That's not terribly useful space. Also, since I mentioned it from the get-go, small SUVs like the Crosstrek and CX-30 could stuff in all the bags more easily without squishing and with more room to spare. They do block your view out the back in a way the Integra doesn't, so with some caveats, it's not entirely a silly comparison to say the Integra has comparable trunk space to a small SUV. It's just that the Civic has a more usable trunk than them all.
All of that said, however, should you compare the Integra to an Audi A3 or Mercedes CLA, it will absolutely swallow them whole. Both have traditional trunks in the 10-11 cubic-foot range. They're quite small. The Integra's trunk is not.