There's actually a lot of plant based meat that are chemical / preservative free, Redefine Meat comes first to mind. As there is a lot of animal meat that is full of chemicals, preservatives, carcinogens, and antibiotics use.

I would only assume most fast food meals, meat ones included, are not chemical / preservative free. That's a western fast food problem, vegan or not.

Lastly, vegan people broadly don't eat plant based meats. Like it get the joke... It's just broadly inaccurate. Meat eaters, people trying to eat less meat, and some vegetarians buy plant based meats.