I have personally never had a diet more than 15% protein. That's what I have currently only because I'm deliberately losing weight at a pretty rapid clip. When I transition, I'll cut back to 10-12.5% protein...still higher than I used to do, but far more will be plant-based and much less meat, with regards to methionine restriction. I'm playing with the idea of glycine supplementation. Straight gelatine is fabulous in Indian-style lentil soups and curries--don't even notice it. It's revolting in yogurt. I'm hoping straight glycine will work in yogurt. I really like it. :)
Overall, I used to eat about 8% protein, 10% fat, 82% carbs, probably half the bad kind. I wasn't consciously controlling fat or protein. I just like carbs.
I will be eating 10-12.5% protein (7% or less from animal sources), 20% fat, and the remainder carbs, with only one once a day refined max and/or only 2 teaspoons added sugar across all foods max. (Added sugar's easy. Refined is a sacrifice.)