Not sure where you are located or what kind of fishing you do. Casting, bait fishing, trolling, etc.
I would think an open 18' side console without a center bench(es) is probably most common in a Jon boat style. For an 18' with a wide open cockpit, it is likely a windshield/walk-thru style boat.
My previous boat was a 15' Klamath Advantage side console with 74" beam. It had a split center bench so easier to move around. It was very stable and comfortable for two of us, even when we both hooked up. They make (or made) an 18' side console version with a split center bench. I suspect Klamath boats are pretty scarce outside of the west coast.
When I decided to "upgrade" to a larger boat, I got a Gregor18' walk-thru. It works great for my use. Gregor is another west coast brand. Sadly, they are no longer made and used ones are likely limited to the west coast.
Sorry if I'm saying what you already know.