If I have a 16ft section of fence to support tomato and peppers, would I be able to plant a maximum of 8 plants. Giving a foot space per plant? Or should I plant fewer?
I think a foot space per pepper plant would work. Tomatoes? Now that is a different question. If you are growing indeterminate types they can get huge and five plants on that 16' fence would be plenty.
Gardening at 5000 feet elevation, zone 4/5 Northern Utah, Frost free from May 25 to September 8 +/- Plant a Garden
The varieties (indeterminate OP/heirlooms) I grow usually are in the 3-4 foot across range. Stagger the plants on each side of the fence and 5 or maybe six at most for the 16'. Peppers can do with a foot between plants like jal says. Don't crowd the tomatoes too much, they need air flow to stay healthy.