You just reminded me that I actually meant to touch on your comment about fiber a bit. Personally, I've never had trouble hitting the amount of recommended fiber in my diet by just eating vegetables and nuts. Now granted, I'm bigger and eat more than most people so hitting about 30g of fiber from those sources is pretty easy for me. But that said, the times my diet has been low on fiber I really haven't ever had constipation issues. I'd say most people are going to get what they need if they're eating vegetables, fruit, and nuts through the day until they feel satisfied after their meal. If you do that and still end up constipated then you can always try tweaking the diet a bit to include more vegetables and less of something else (there's not really any one proper ratio of protein, carbs, and fat in the diet for everyone), or maybe resort to a fiber supplement if needed.

Really though, it's all about trying different quantities of food and seeing what happened. You can start with roughly equal amounts of protein, carbs and fat from better quality foods and see how that goes in terms of weight loss, muscle gain, mood, energy level, how long you go before feeling hungry again etc. From there tweak it a bit and see how things change. It could help to keep a food log where you write it all down as well so you can go back and compare. But that's if you're really interested in finding out where the sweet spot in your diet is. If you don't want to over think it that much, just focus on real food and make sure you get plenty of protein and fat in there. Pretty much everyone will see benefit from doing that.