The most practical tire for mild off road use is the 26" x 2.1". If you are tall, you can use larger 700 cm or 29" diameter, but don't decrease the cross section below 1.75". Fat tires, 3.1" & above, are more of a fashion statement than a comfort device, IMHO. They are useful for fluffy beach sand and powder snow. Fat tires are reported difficult to get off the rim out on the road when you have a flat. I can change a tube in my 2.1" in 30 minutes. If you're going to go fast you need a suspension on rough roads, but under 10 mph the tire will soak up the bumps. Suspension costs about $1000 extra.
What size body do you have? Bike frames come in sizes and buying the wrong one is uncomfortable.
The internet sales bikes as juiced have a huge disadvantage. If there is a problem, you call the company and request help. Then you fix it yourself. If you buy from a local shop, they should be responsible for solving problems. Electric bicycles are not yet trouble free, and buying what a shop within driving distance stocks helps address that problem. If you are close to Dallas, looking around in those shops should be the first priority. If either is under 66" tall then a proper sized bike will not be in stock, but otherwise you should find something that fits.
The base page without the forum suffix has a shop finder, if you put in your zip code. Others may be found on search engines.
Some brands use cheap "steel" for spokes and break a lot of them on rough roads with heavy loads. Look for this problem on the brand forums for any brand you consider. People obsess over 13 & 12 ga oversize spokes, but actually 14 ga is fine under 25 mph if the steel doesn't contain copper or zinc.
