My wife and I are heavier riders (215lbs and 280lbs), but we still want to ride long road rides for fitness, topping out at around 60 miles and 2000-3000 feet of climbing. Our biggest concerns with ebikes are not killing the battery before the ride is over, and having enough power/torque to provide assistance on the steeper climbs. What key specs should we look for and what bike models lead the market in those specs?
I'm 6' 2", 260# and one of the biggest factors for me when bike shopping was the weight rating. Most e-bikes top out around 300# which includes the combined weight of the bike, rider and cargo. Pay particular attention to the quality of the rims and spokes on the bikes you look at. Many have a 32 spoke wheel. Personally, I wouldn't look at anything with less than 36, 12 gauge interlaced spokes. I'm sure others will disagree with this but over the last 40 years, I've broken spokes on every bike I've owned with less than the 36/12 format.
Another consideration is whether to get a step thru or high bar frame. At present, you may have no trouble mounting a high bar bike but consider the future. At some point, you could develop joint or back issues leaving you unable to ride your expensive high bar ebike.
I admire your lofty goal of 60 miles and 2 - 3000 foot climb! I doubt you will find a bike that will fit you and achieve that on a single charge. Your best bet would be a bike with a mid drive motor for better climbing ability and carry a spare battery.
After shopping for almost 2 years, I bought a Pedego Platinum Interceptor. I chose the mag wheel option for it's 400# weight rating. The mags add little or no weight to the bike and completely eliminate any spoke issues. Although at 72, I can still swing my leg over my Trek MTB high bar bikes, I don't know how much longer that will be the case. For that reason, I decided on the step thru frame.
To put it in perspective, the Pedego has a 500 watt rear hub motor with a 15 AH battery. With a total weight of bike, rider & cargo at 340# and a climb of 800 feet, I can get 55 - 60 miles on a charge using the lowest assist setting. At my age, any more than that would take all the enjoyment out of the ride. A bike capable of doing more would be wasted on me.