The OP here is extremely overweight for their height so any bike they choose will need gears, unless the places they intend to ride are absolutely as flat as a pancake and very sheltered from the wind.
How far off the ground you are depends primarily on how long your legs are and you don't have any choice in that matter. I would strongly advise against buying anything with aggressive geometry, a relaxed upright frame sounds the most suitable. With wheel sizes I reckon 26" is probably the best combination of ride quality and manoevreability.
Small wheels don't make the riding position any lower since you still need ground clearance under the pedals. The main benefit is making the bike shorter in overall length therefore more compact and easier to store. The downside is worse comfort for a given tyre width.