We have had lots of cats over the years and 5 at one time - all rehomed and some feral. In our experience they need time to settle, but the best thing is leave them to it and they find their own pecking order. At the moment we have two rescues and one feral. The feral has turned out to be the most loving, one is a spitfire and the other is a lazy fatty. Spitfire and feral have occasional noisy conversations, but not a drop of blood ever spilt. The dog is also in the mixture. If I was you I would take the other cat.