I’d suggest taking some time to read about personality and health traits of each breed you are considering.

That perfect, cute little thing can be a real problem if it isn’t the kind of pet you expected.

I, personally, know nothing about little (i.e. “cat-sized”) dog breeds but I know that in larger breeds, personalities and quirks vary dramatically so just take the time to find a website with that kind of info and read, read, read.