Proximity, quality, availability of products and ease of service all play a role in selecting a grocer. I have tried two of the three available in my area: King Soopers (Kroger) and Walmart.
My two cents on the difference is that Walmart has no fees for pickup, but there is no ability to indicate what state of ripeness you want your produce in. King Soopers offers more specific selection on produce, but charges for picking up.
You’ll have to decide what works best for you. Below are some links to on-line grocery ordering platforms. Look them over, see what you like, and try a couple. Most will offer you a free pickup for your first order even if they normally charge.