On More kids, anecdotally, it really does help. Especially in pandemic time.
The extra effort after one is pretty much a wash, but I see so many parents that spend so much time entertaining, and hanging with their kid. There's nothing wrong with that but it's not at all how we were raised.
I think there's something really beneficial to just going out into the world with someone who knows about as much as you and exploring. No one standing there telling you the answer or why right away.
You can play with your kid, but you'll never be let's get sticks and play pretend Zelda for 2 hours focused like two kids might.
Mine craft buddies? For sure.
Rainy day monopoly? Definitely.
Homework help? They do that too though sometimes need an adult. Nthe little one is really good at math and the older is a better reader/speller.
When we go to dinner, my wife and I can sit across from each other and enjoy a conversation and our kids usually talk/play games/do art together.
The amount of time they spend together takes a burden off of being a parent that I see my friends and other parents carry.
They are more like roommates to us than massive chores because we have time to do other things in life without feeling guilty because there is a board child that need socialization and attention.
They are kids, they need adult help and input but they don't need to be entertained every minute of the day.
I also am willing to factor that being able to afford 2 children in the city may hint at other problems we don't have. I recognize that's generally quite the privledged place to be and don't take it for granted.