What not to plant together in a container raised garden???
Are tomatoes okay next to potatoes and peppers ???...
Certified GKH Gardening Expert
These articles will help you.
Unfortunately, companion planting has not withstood the test of scientific studies. That said, giving a plant adequate spacing for root growth and to prevent shading of adjacent plants is important.
Some recommend planting top-growth plants like tomatoes next to tuberous veggies like potatoes, carrots and beets. If you are hoping to plant your veggies close together, look up Square Foot Gardening. I found a webpage that has good info on this approach. https://www.ag.ndsu.edu/publications/lawns-gardens-trees/the-facts-of-square-foot-gardening