Honestly that depends completely upon how the cats have been brought up by you from kitten to adulthood.
By nature cats are independent animals. They are solitary animals. They like to be left alone. They also don't need the company of other cats. In fact in nature, cats are territorial and when one cat crosses into the territory of another cat, fight breaks out.
Moreover, cats domesticated themselves. When we became farmers in ancient times and settled down, we stored our grains for future use. The rats started to come to eat the grains. And the cats came to eat the rats. So there started a mutually beneficial relationship.
Long time passed and slowly cats started to get domesticated. They started to have fondness for humans and more tolerance towards each other.
And then started the phenomenon of cats taking birth in human homes, with no exposure to nature. And such cat's behavior is bound to be much different from their distant wild cousins.
So, now coming back to your cats, their behavior completely depends upon whether they were born in human house and grew up with humans or they are rescue cats and later adopted by humans, irrespective of the love and care they are currently getting.
Also cats don't fight doesn't necessarily means that they are friends. It can very easily mean that they just get along. They get access to food, water and clean litter box. So they know that if they get along, it is beneficial for them.
If the cats sit or sleep side by side, even being adult they play with each other, they groom each other, these are the signs that they are friends, and not just getting along.
Now coming back to your question, cats have excellent memory, they mark their territory well and they will never get lost.
So, if they are with humans since kittens, they don't have much idea about outside. So other than satisfying their curiosity, they will mostly stay home, eagerly waiting for you. And since there is enough food, water and clean litter box, you need not worry. As they have little idea about outside, they will be always wary of outside and will be never eager to leave the comfort of home.
And, if they are rescue cats, they will always spend some of their time outside, as they have grown up being completely aware of the whereabouts of outside. They will show little willingness to always stay at home. But as I said that cats have excellent memory, they mark their territory and never loose their way, they will always come back. It is because they know that at home they have abundant supply of food and water which is not there outside.
So either way you are not going to loose your cat.
The only cause of worry may be how safe is your outside. If you live at rural region, then are their wild animals outside, and if you live at urban area then is their dangerous vehicular traffic outside.