Welcome to COL.
The fact that you have posted and are asking questions means that you obviously care a great deal.
I've been around dogs all my life and have no fear, but I imagine owning one for the first time could be rather a worry.....Just the same as having your first child to care for.
Cockers aren't vicious, they are incredibly loveable. We have a labrador and a cocker and they both try to win on the attention stakes....LOL. They both adore being fussed and stroked and kissed.
Puppies all play bite, until they get their adult teeth through, but that is normal puppy behaviour. They love their family, and are a delight to own.
Maybe it would be worth visiting friends with dogs, dogs homes etc, to get used to strange dogs.
I don't have any knowledge about cats with dogs, but plenty of people have both and usually the cats are the boss
Good luck with your decision, and make sure that you do plenty of research and reading, and if you do decide to go ahead with a puppy find a good, reputable breeder.