White Bird of Paradise (Strelitzia Nicolai) isn't a palm. Its an herbaceous plant that comes from South Africa. Yes, you have more than one plant, because like bananas, these plants sucker and make lots of offsets.
Your plant is extremely juvenile in spite of what you consider being a large plant. These typically reach heights of 18-20+ feet and will not flower until more mature, like these pictures.
You should just leave all the plants alone in the container until its gets crowded and root bound then step it up. Unless you live in USDA climate zone 9B and up (or 9A with an extremely good microclimate) you should not plant this out, a freeze will set if back
