I wonder the flipside as well. I'm extremely confident a healthy vegeterian or vegan diet will be generally a bit healthier than a meat-heavy alternative. But I believe you can overdo it too, like if you eat enormous amounts of hard raw foods and leaves with low calories that might not be all that great for your gut either? (our gut is probably adapted to eating cooked stuff).

My armchair recommendation: avoid processed foods (but you can have processed if you're really confident what goes in isn't harmful or just very occasional I guess), eat a good amount of salads and veggies alongside some cooked main course, like beans, rice, tofu, etc.. Eat some fruits throughout the day, and a reasonable amount of water. Chew your foods well. Exercise, bla bla bla, you know the drill ;)