“Random crap” is what’s used in agriculture as well, if you buy a big plastic tub, it won’t leech more into the soil than your coke bottle already did. There’s only so much plastic that can leech out and planters can be used for years, the plastic you’re using around your house gets thrown out in a week or two and replaced. Much higher chemical content there.

And you can absolutely use store bought potatoes, they are clones, there’s no difference between seed and regular potatoes. At most, there might have been something done to prevent sprouting for a bit, but that’s it. You can simply wait for them to sprout, if that’s a concern. You know how I know? I’ve been growing “old” food potatoes in pots for years. Works just fine.