I'm a bit confused by that quoted bit since whole-food plant-based diets are an entirely separate concept from plant-based meats. Whole-foods plant-based diets ential using whole foods like beans, potatoes, lentisl, etc. in dishes

For the second half. Nearly everything is tested by the FDA. You can find plenty of naturally occurring things like citric acid from citric fruits having been given a GRAS referencing studies to determine how much may be too much.

Natural does not nessaraily mean healthy. For instance, Tobacco isn't exactly healthy despite it being naturally occurring and having been used for a long time

Are plant-based meats the healthiest things in the world, no, but are they worse than meat, the current evidence suggests they are likely better health wise in that comparison