My understanding is that lettuce takes up a lot of room to grow, but u can grow tomatoes & cucumbers in limited spaces. Both will grow in those vertical grow boxes where u put a piece of trellis in the box so that the plant can grow upwards.
I know zucchini will grow in a small space, too, but it gets out of hand quickly, so isolate it from ur other veggies, as it tends to take over wherever it is planted--also, it is very hearty, & produces a lot of veggies from each plant, so do not overplant that one.
Peas r delicious when fresh, & they r only a small plant, so u can probably grow them in a limited space. I believe it is the same with green beans.
We have, in past years, planted all of the things I mentioned, & had them grow really well. I do not really know that much about gardening, so I do not know what is slug resistant & what is not, but I do know u can put out stuff that kills the slugs if there r too many. I have also heard that u can buy ladybugs (yes, ladybugs) & release them in ur yard, & they will help control the small flying things like aphids & gnats.
I hope that is of some use to you.
Good luck, & happy eating!