Help Setting Macros

YMMV, personally I only look at calories and protein. You need the calorie deficit for weight loss. So in that regard, I don't think the macros matter. Use more calories than you take in and you'll lose weight.

I've lost over 50 pounds and have been maintaining for a while, and the only macro I look at is protein. My macros are set to 50% carbs, 25% fat and 25% protein. I've no idea how much fat and carbs I take in tbh, though I generally know the protein to the gram. I want higher protein, close to 1g per pound lean body mass which for me means 25% calories from protein, because of a) resistance training, b) slight calorie deficit, c) getting older. Generally I find while aiming for those two goals of higher protein and calorie deficit, that keeps carbs and fats from getting out of hand.

You'll find that having more protein is satiating, which helps with your calorie goals.

Calories determine weight loss . . . specifically, eating fewer calories than you burn in all ways (breathing, heartbeat, digestion, job, hobbies, formal exercise, etc.).

Macros are about nutrition, which mainly affects health, energy level, body composition (muscularity, to some extent), and that sort of thing.

Nutrition can matter to weight loss indirectly. Sub-par nutrition can spike appetite, make it harder to stick with reasonable calories. Sub-par nutrition can sap energy, making us rest more and move less, so burn fewer calories than we might expect. But the direct effect of those things is still via calorie intake/burn balance.

If you only care about weight loss, you can just watch calories. If you notice energy declining** or appetite spiking, consider improving nutrition to see if it helps. (** Energy can decline if you try to lose weight too fast, too, no matter the nutrition.)

If you care about general health and not just bodyweight, then nutrition matters. Still, if you're materially overweight, that in itself is a health risk. If you're not starting out diagnosed (by a doctor) with some significant nutritional deficiency, it's fine to focus on calories first. Once you figure out how to stay full and energetic on your weight-loss calorie budget, you can start working on improving nutrition, if you want to.

In the technical sense that our bodies can't manufacture them out of any other nutrient, protein and fats are essential macronutrients. We need to eat some minimum, to get good nutrition. A lot of people get enough fats without focusing on it, so mostly pay attention to protein. Carbs are more flexible . . . though some people find that they need carbs to have a good energy level, or that carbs spike their appetite. Those people may want to manage carbs more closely, but you'll figure out experientially whether that applies to you. (Obviously, if you have some condition like diabetes, you'll want to manage carbs carefully.)

The MFP default macro percentages are a reasonable starting point for most people, as long as they're not super-aggressively cutting calories to lose weight very fast. Too few calories means too little nutrition, even if the percentages are OK. There are many good reasons not to lose weight fast, so shoot for 0.5%-1% of current body weight per week, with a bias toward the 0.5% unless severely obese.

TL; DR: If weight loss is the big deal for you, worry about calorie goal first. Tweak eating subjectively if needed to stay full and energetic on that calorie level. As long as you don't have a pre-existing relevant health condition or doctor-diagnosed nutritional deficiency, just eat in a generally sensible way, and you can worry about nutrition details later.