You fail to give vital information. Are you growing 250 pound Great Danes or 2.5 pound Chihuahua? Do you have 100 acres or only 10 square feet.

1 tepin
2 sweet banana
2 lilack belle
1 chocolate belle
5 Pasilla Bajio

I am not great with dimensions. I don't want to hog garden space, as we have other crops. If the plants are too close together, will their roots have problems, as they will tangle,competing for the same nutrients?

Two feet between plants will give them plenty of root space and above ground space, though some of them may overlap a bit. I think that seed packs will tell you to plant a little closer but that is because (for picking purposes) it doesn't matter too much if plants of the same vareitey overlap each other alot.

I would save the plant food spikes for container grown houseplants. For fast growing garden vegetables you want evenly spaced nutrients that the entire root system has access too. You could go with liquid blue stuff periodically, or mix granular garden fertilizer, or slow release pellets into the soil before you plant.

Go very light on any fertilizer. Chiles need from 1/4 to 1/2 the fertilizer that tomatos do.

It is always good with chiles to underfertilize.