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You'll know it if the play-fighting escalates to "proper", the expression "the fur was flying" is surprisingly a literal description of cats fighting.
The noise they make is pretty terrifying as well, you'd have no doubts at all that srsbsns is going down.
I've always let my cats have the run of the house whenever they feel like it, they're fine. They spend most of their time sleeping anyway so they'll be doing relatively little fannying about knocking shit over while you're sleeping. It's probably worse to shut them into a room when you're not around because they'll claw everything near the door into shreds trying to get out. Worse still if you shut them in the same room as you as you'll be able to hear them doing it and will go insane.
Mine never have, Higgs knocked over plenty of glasses (trying to drink from them) when she was a kitten, but she grew out of that.
You'll know it if the play-fighting escalates to "proper", the expression "the fur was flying" is surprisingly a literal description of cats fighting.