I’m jealous. Perfect time of year to go there. Expect it to be a bit chilly. Bring some warm sweaters. Although you maybe lucky and get shorts weather. But prepare for both.
The driving will be amazing but I’d bring some good walking boots and explore some trails.
As for food... I’d avoid any chain type restaurants. Quebec City is Known for their food and with the exchange rate you can eat like a king. Try small local restaurants. Try order in French and don’t rush.
https://www.quebec-cite.com/en/what-to-do/activities-attractions/ideas/fall/