re: The importance of 200g of protein/day.

250g of protein is 1000 calories. That’s exactly 40% of your intake leaving 60% (the majority) for carbs and fats. It’s really not that hard to hit 250.

As for as 200g, it’s just an easy benchmark. Unless you’re Shaq big, no one is losing muscle mass eating 200g a day. But, if you want to be exact, it’s more a function of desired body weight than just a hard 200g rule. You can get similar results with less as long as it’s right for your goals.