I thought you've been here long enough to know the answers to these already.
Your BF% determines how much definition you have.
If push-ups are a real struggle, you'll use type II (strength) muscle fiber , but once the muscle develops enough, it will switch to utilizing more type I (endurance) fiber. You can probably delay this a bit by using plyometric push-ups, but not forever.
You can use bodyweight, if that floats your boat, but again, it comes down to if the weight does not create the stress needed to recruit type II fiber, it'll use type I fiber.
In short, what you cite is certainly possible. Will it give the results you want? You didn't state any goals, so I have no idea.