If you are looking into getting another canary I have some input. I have four canaries (both genders) in the same cage and I have not had any problems or aggression. I feel that if you do have multiple canaries (this goes for most birds) in the same cage you need to have a
big enough cage for them to have space, and enough perches, toys, and places to go. Canaries are territorial so it's important to have a
bigger cage so each canary has "their own space". My birds have
multiple food bowls on the bottom of the cage so each bird can eat alone if they wanted to, but sometimes they like to eat together. But make sure you have the time, money, and a good place in life to be able to do what you need to to take care of of everything.
-If you were to get another bird and they were to fight or show signs of stress or aggression please take them out and keep them in separate cages. If you let your birds out to fly around the room, you could let them out together and maybe they will get along.
-As my canaries are rescues, they do enjoy having the company of others and being able to fly, chirp/sing and interact with each other. But please remember that all birds are different and have different personalities, this could cause a problem. You could always keep them in separate cages do they could still interact without a problem.
When my canaries go to bed, they all have their own spot they like to sleep in. One of them likes to sleep on a platform perch in the corner of the cage. One likes to sleep on a rope swing. The other two sleep on a normal wooden perch.
Anyways, please do what you think is best for you and your bird
Thanks for reading this and I hope it can help!