When it comes to weight loss there is only one hard rule - calories in must be less than calories out. Then how to achieve that differs. Often going high in (quality) protein is preferable, especially if training. You will still need plenty of carbs and fat as those are what gives you energy, but you can skew the ratio towards protein.

If you want to go the shake for lunch path you may want to look for meal replacement shakes rather than training shakes. It is however a field I'm not very knowledgeable in. But that is how I would do it, if doing shake. Or if you just want a lighter lunch, something semi-fluid, I cannot recommend enough going down the yoghurt/quark road. Combine with some muesli and fruits/berries. Quark is the high protein option (10%+ by weight) but is much firmer. If you need even more protein add eggs.

You will still need plenty of carbs and fat as those are what gives you energy, but you can skew the ratio towards protein.

OP, I just wanted to point out that this line from another comment is confidently incorrect. You do not need carbs. You may want them, you may even prefer them. But "need" is straight up wrong; our bodies operate just fine in a complete absence of digestible carbohydrates. You do, however, absolutely require healthy fats (saturates and monounsaturates; processed PUFA are seriously bad) and complete protein. Sources: "Good Calories, Bad Calories," Taubes; "Fat Chance" and "Hacking of the American Mind," Lustig; "Body by Science," Little and McGuff. There are loads of books you can read to get the answers to your questions rather than relying on Internet hearsay.

It sounds like, at least in part, sourcing is one of the issues with ingredients, and that you've been getting conflicting information because people leave out that context. Peanuts can be awful for you, but sourced with care, they're great! Oh, right, how do we know our food supply integrity? Well, now we're actually getting into the meat of the issue. No pun intended.

None of this answer your questions, and that was intentional. Also, sorry. But I did provide you with some excellent sources to start getting answers that are not a bunch of unsubstantiated Internet hearsay. You have one body, and it happens to carry your brain. Invest in it like your life depends on it.

Edit: wrong book title

Consider looking into Soylent/Joylent equivalents (Queal, Huel, etc.). The macros will be better than a slimfast with more fiber. It will come as a powder you'll need to mix. But nutrition wise, will be more balanced than protein powder shakes and you can get them in vegan varieties. I use a gram-accurate food scale to measure out my portions and I mix it with almond milk.