Not specifically applicable to hot peppers but to container gardening - of any type - in general:

• Topsoil or garden soil in a container is NEVER advised! Because container gardening is more or less a closed system (compared to inground gardening), you cannot follow similar gardening principles and expect similar results. You need an aerated, fast draining and preferably durable, dedicated potting medium. Can't get that from garden soil or topsoil - too fine a particle size, too dense and with insufficient aeration. Drainage tends to be very slow/poor, a high PWT develops and the plants suffer.
• Coffee grounds do not provide sufficient "essential nutrition". They are primarily a nitrogen source.....everything else is not present in large enough concentrations to be of much value. And because the ideal container potting soils contain no actual "soil", there are not the necessary populations of soil organisms present to efficiently convert any raw organic matter into plant accessible nutrients. So in a container gardening situation, even the N in the coffee grounds is not readily available. You really need a water soluble or fully liquid all-purpose fertilizer with trace elements -like Dyna Gro's Foliage Pro - and there are very few organically sourced ferts that can address those qualities.
• Vegetable cooking water can supply some nutes but not enough to rely on.

The best practices to "make a significant impact on the overall health of your plants" is to follow accepted container gardening practices - use a dedicated container or potting medium and fertilize with an all-purpose, full range water soluble or liquid fertilizer. No household byproducts are going to provide much assistance otherwise. Well, urine works well but must be diluted and many have issues using urine on any edible crops :-)

Thank you for the detailed response Gardengal! Sounds like you have done your research.

Better to use vegetable cooking water when cooking something like rice or soup, or else use it to make a Velouté sauce for the vegetable, like my grandmother did. You can use potato cooking water when making bread.