The hissing is when others come to the house.
Yeah, strange people can freak a cat out. Imagine being a small furry critter, and in come these huge things with their stomping feet and loud voices...
Do you or your guests force the cat to interact when there are strangers around? If someone roughly ruffles her fur when she doesn't want it, and she hisses and scratches that is
NOT unprovoked, from her point of view. Does the cat have a quite place in the house to retreat to?
Do you keep her nails trimmed?
She mostly just meows (sometimes loudly) at my wife and me.
So... you were concerned that your cat might be feral. Meowing at people is not feral cat behavior. Cats don't meow much in the wild. Adult cats do vocalize at each other, but they usually don't meow. Meowing is more typically a behavior between a kitten and its parent. Domestic cats meow to get your attention, like they'd meow at their mom when they were kittens. It is totally normal - some breeds are extremely vocal.
She likes scratching furniture when I come home from work.
Cats absolutely need to scratch. It is how they keep claws healthy, provides muscular stretching, and is part of basic scent-marking behavior. So... what non-furniture surfaces do you have for your cat? Where are they placed?
The timing may or may not be interesting - she may simply tend to wake up from a nap when you come home, and it is just part of routine. But, there may be other things - scratching can be part of stress relief. Do your dogs get very active when you come home? That may make it loud and chaotic in the home, and the cat may be scratching to relieve the stress that generates - a physical way to blow off steam, if you will.
She hates being taken to the vet (or anywhere for that matter), so I'm not sure if the vet will be able to get a fair view of her behavior.
If you thought dogs are territorial, they have nothing on cats. They don't usually like going out and about from their territories like your dog may. Plus, the vet's office smells of
every other animal that's been through, and many of them are unwell, or scared. So, big stressor, there. Lots of cats hate going to the vet.
So, you make a great point, for which there's a solution - get a house-call vet. They exist. They cost a bit more, but they may be a good option for you to get someone to come in an see her home environment, and her behavior in it.