I'm trying to eat food rich in proteins and poorer in carbs when feeling slightest hunger, so most of the time I'm well fed up. Isn't it better to base the need to eat on that, plus a dose of whey for the surplus, and not on some artificially calculated figures?
No.
The body tends to crave simple carbs when you're hungry.
Counting calories (or at least accurately estimating, ideally based on experience) is really the best way. You may well be very surprised if you actually count your calories one day. Some foods have a surprising amount of calories in them.
As Totz has said, losing fat and gaining muscle are almost impossible to do properly, even with the likes of Intermitent Fasting or carb cycling. In simplest terms, you ideally need a surplus of calories to gain muscle, and a deficit of calories to lose muscle.
If you want to bulk up, then you need to eat - I spent years bulking, and sometimes the amount I had to eat was uncomfortable. As the saying goes.. "if you want to be a 300lb man, then you need to eat like a 300lb man"
Likewise, dieting (for fat loss) is uncomfortable, as you eat less, and so feel hungry a lot of the time. I guess the same saying applies - "if you want to be a 180lb man, then you have to eat like a 180lb man!"
Pick muscle gain or fat loss.
A lot of people cut first, down to 10-15% bf, then bulk.
Can I also just add, dont forget to drink. If you wait until you are thirsty before you drink, then you are already dehydrated, and that can lead to health issues.
At the end of the day, bodybuilding is a lifestyle, not a quick fix. (Unless you're a Hollywood actor with a dietician and cook and personal trainer!)