That's the great thing about cats. As long as they were raised indoors they don't care about a lot of space. They're just as happy running back & forth across the bed, in circles around the kitchen or bathroom as they would be in an open field.
Although cats are predators, they're small animals so have predators out to get them too. So they're quite happy hiding & stalking in small places. Cats are sneakers & stalkers, not open field animals.
Chasing the shadow of their tail, each other, a fly in the house, or stalking a toy under the bed doesn't require much space.
All the indoor cats I've known spend 90% of their time on or under the bed, sofa, or a chair, & ignore the rest of the place except to pass through. They'll be attracted to the area of the most activity, or what's the most comfy for them.
When I moved into this very small place from a much larger place, my old cats didn't seem to notice or care that the new place was only 1/4 the size of the old place. My newer cats are fine here too.
In my 1 bedroom upper flat, the bedroom is for storage, tools, & workspace. I keep the door to it closed to save on heat & AC. There's sharp objects, small things they might swallow, or stuff they think are toys I wouldn't want them to play with in there, so they never been in there.
The rest of the place is set up studio apartment style. The bed & living space is on 1 side of the room, & the kitchen is on the other side of the room. The only other room is the bathroom. So the space the cats get is rather small, but they're fit, healthy, get plenty of exercise, & happy.
I keep a couple of large empty cardboard boxes stacked in the corner for them to scratch to death. As long as they enjoy scratching that, they won't scratch anything else. The cardboard bits they scratch off are easily swept off the carpet without having to pull out the vacuum. If I'm not expecting company, I'll just leave them there for the day. When the boxes get too raggedy, I just throw them out & get more free boxes.
I cut holes for them to play inside the boxes. They love to sit on top of them too.
I keep them active with playtime & toys. But their favorite toys are plastic bottle caps, twist ties off bread wrappers, & noisy crackly plastic wrappers. They chase each other around too.
In a small place you might be better off with 2 cats so they can keep each other occupied when you're busy or not at home. It will also prevent a cat from getting too nuts or weird by only having you as company, & keep them more sociable. They won't ever get too lonely with another cat around.
Beware though, 2 cats won't always get along with each other & you'll be stuck with a violent or depressing situation. It's best to get 2 very young ones, preferably from the same litter but of opposite sexes. Same sex cats tend to view each other a rivals or competition. If they're raised together since babies, they've learned to get used to & attached to each other. If they're from the same litter they even smell similar & their litter box dropping smell similar so they won't get annoyed over each others scent.
Some people had no problems mixing different cats of different ages & sexes together. But most of those cats lived with other cats a lot before. More often than not, mixing same sexes or older cats together, especially in an apartment, ends up disastrous. So unless the cats were used to living around other cats a long time, get a couple of the same sex, young, from the same litter when possible.
But there's also the attached cat, where they became attached to another cat or kitten but were split up. Bitter that the cat lost it's friend, it does not want to be around another cat, it wants it's friend back.
I had a friend with a 5 y/o male cat. He took care of a kitten for a few months until they could find a home for it. The male cat loved the kitten, cuddled & played nice with it a lot. But when they found a home for the kitten, the adult cat was devastated, turned bitter, & angry. He was never the same again after taking the kitten away. He would not get along with another cat again either.