Ive done the fast food gig a few times in my life and it really depends on the individual place. Local places can be pretty chill purely in terms of vibes but dont expect to be able to live off of your wages unless you're a manager, which you arent gonna be unless you kiss ass. I was a fry cook at McDonalds for a while until the franchise owner sperged out at me randomly one day and I knew it was time to find a better job after that. I worked at KFC after that, and I was getting paid pretty badly but I still have fond memories of it overall. It was pretty laid back and we got a free meal from the buffet every shift, and since I was a closer I got to take home a ton of unsold chicken most nights, and stuff like biscuits, sides and pot pies (BTW KFC pot pies are actually delicious, especially if you leave them in the fridge over night and heat them up in the oven. Definitely the best thing on the menu and I think a lot of people just don't know about it.)
OTOH I have nothing but horror stories for the time I was a dishie at an actual restaurant. That was genuinely the worst job I've ever worked and I reccomend you GTFO out of any place that you apply at and tries to offer you that position.