What type of flowers can I plant in large outdoor planters to keep the

https://davidsuzuki.org/queen-of-green/keep-cats-garden/

Marigolds keep out most pests. I don't know about cars but usually rabbits and small critters.

I'd put a layer of 1" chicken wire on the top of the soil after you have planted, or use a handful of plastic picnic forks poked into the soil, tines up -- they come in colors ( black is the least noticible ) -- and available on Amazon in 'BULK'

About a dozen years ago, I bought a 50 foot roll of green plastic coated wire fencing, it's 4 feet tall with 2 inch openings in the fencing. I used it to make cages to place around planters to prevent the deer from chewing off the plants. It may not be overly attractive, but it works, & it would prevent cats from getting in your planters.

CACTUS will keep that furry balls out!!! lol. I can't help........sorry

Peppermint might be a good option. It's rather bushy so good luck them trying to dig in that soil.

Thanks for all the tips. Will be trying them.