I have 4 and they wrestle, but rarely fight. Fighting includes hissing and claws out, which only happens when one of them goes too far (usually the male, who is the biggest of the lot).

I do love that our smallest cat is picked on the least, because when another cat picks a fight with her, she never gives up. These wrestling matches are usually a minute or so, but she will hound and hunt them relentlessly for up to 2 hours after, long after it stopped being fun for the initiator. We call her the boss for a reason even though she is an adorable little fluffball.