I'm 6'3" and 265 lbs (down from 287 lbs when I started biking again at the end of summer). I've had pretty good luck with my 2016 Radrover. I added a larger Sunlite cloud-9 seat 11.5 X 12.5 size and a Suntour NCX SP-12 suspension seat post. I didn't have to adjust anything else for a comfortable ride. The longest ride I've taken with my ebike was 36 miles at PAS 3 and my legs gave out before the battery did (just under 20% battery life). I use the ebike mostly for commuting to work 13 miles round-trip on paved main and side roads. I'm probably 290-300 lbs with cold riding weather gear, large back pack, Topeak Rack bag with Panniers, work cloths, lunch, and cool weather gear for the afternoon.
It is mostly a drop in elevation to work of 5400 ft down to 4900 ft and I maintain speeds between 20-23 mph at PAS 5. My speed range heading home is between 15-17 mph at PAS 3-4 depending on how stiff the headwind is that day. I have no problems maintaining 18-19 mph at PAS 3 on level ground (again, any headwind will drop my speed).
One thing I really like about my 4" fat tire bike is it can transition from paved road, bumpy dirt lots, dirt trail, rocky trails, mud, and sand on the same ride. If you are planning to ride at all in the sand, fat tires with low PSI make it possible.
Which ever ebike you pick, I would plan to upgrade the seat post to a suspension type like thudbuster, cirrus body float, or Suntour NCX SP12 (assuming it is not a full suspension bike). I would also lean towards a bike with:
- front suspension forks
- larger tires to fat tires if possible to smooth out the ride more (cracked paved road are very bumpy at 15-23 mph)
- PAS and throttle
- opt for a larger battery capacity if available because you and I seill always use more e-power because of the extre weight
- plan on upgrading the seat and seat post. My seat Suntour seatpost is 27.2mm/400mm long. A 350mm lenght will work; but, you will be at its max height if you have long legs.
- make sure the bike comes with or has places to add accessories like water bottle(s), fenders, and racks.