If you are riding slow, then you don't want a hybrid or a road bike IMO. The Sun Retro CB seems the right frame with the better style of bars that have a large sweepback. But the one I looked at didn't have gearing. Regardless of flat or hilly, I wouldn't ride a bike with out at least 3 speeds help with even the modest of changes in surface conditions. Whether that is grade or or brief times you might have a softer surface to ride.

All those bikes are going to be heavy. So if you are in rolling terrain or mountainous terrain, you'll get tired very quickly.

You might even want to consider a e-bike. That might let you ride and keep up with some friends that are still more active. Or at least let you ride further for longer and get the longer amount of cardio exercise you need.

Also, I assume you are looking at the step through versions of those bikes. Realize you might be able to just lean more normal looking bike over enough to get your leg over the saddle or top tube. Even on my road bike today, I'm usually sitting in my saddle at stop lights with one foot on the ground, the bike leaned and the other foot on the crank ready to go. And my saddle is very high.