Q.Fruit growth in newly planted plants?
Should I allow newly planted plants (tomatoes, peppers, erc.) to start producing fruit before the plant is fully grown? Concerned that plant will put all its resources into the fruit and not plant growth.

If the plants have just gotten into your garden, I would remove that first pepper.
Depending on the variety and it's growing conditions etc., you may only get a few peppers per plant.
https://www.gardeningknowhow.com/edible/vegetables/pepper/growing-peppers.htm