I think, like most things, keto/carnivore is highly individual. When I first used keto/low carb. I felt like shit and looked skinny fat. I think it was because I had to sort of reprogram myself to get over the fear of eating high fat.
Once I got the ratios right, which for me is similar carbs to protein in grams but obviously about double fat in terms of calories to protein, I was able to get lean and retain muscle.
Im just now learning how to use sodium which I also always thought was a no no.
Whenever I tried high carbs/low fat, it works great for about a month or so....then I start to look like shit after that. Some people just cannot tolerate low carb though. It can be difficult if you're not ready for the initial depletion.