I've only had one experience with multiple cats. We've had a male siamese for years. He was always a solo cat, and was intact at the time. But I saw an elderly siamese at a rescue, and offered to foster, and adopt if my guy would accept the old man.
It took some time, but the old guy (Beau) was such a gentle soul, he was mostly blind and never showed any aggression, no matter what TicTac did. Eventually they did become buddies and I'd catch them sleeping together on the bed or on the couch...it was very sweet.
Unfortunately the old guy passed away after 2 years. I think he was very happy being loved in his twilight years.
We really have a full house now, so haven't considered getting a second cat again.