Different eras of road bikes brought fashionable changes in frame geometry, but as a general rule, a cruiser has a more laid back seat post and longer wheelbase. Fit is most difficult to achieve with a road bike because they aren't built for comfort as top priority and what works to transfer power efficiently does not often match what is comfortable. The idea behind them is also that you are powering enough that you don't support much of your weight on your hands, but the geometry makes that difficult to do unless you are heavily using your leg and core muscles as you would when riding fast (that you're not supporting much weight on your backside is why the saddles are so often recreations of devices used during the Spanish Inquisition). That's also the reason for the drop bars—to allow for more hand positions to relieve stresses, particularly on longer runs and to allow for different postures to match a change in topography. Cruisers are designed for comfort at the expense of efficiency and handling and are not generally expected to do long rides.
It sounds like you want the shorter reach and more upright stance of a cruiser, but something like the more efficient pedaling geometry of a road bike. I am much the same way. My favorite bike that I've ridden is my modified 93 Giant Innova, which is an early hybrid with a strong and reasonably light chromoly frame (mostly a rigid mountain bike with larger and thinner 700c wheels and tires). It's a hair on the small side for me, but I can easily dismount while moving. It is versatile, comfortable, and surprisingly fast—not as much to keep up with roadies, but I have to hold back whenever I ride with anyone else. These types of bikes are usually pretty cheap. Here's what it looked like originally (actually, this is a slightly larger one I picked up to electrify) and what it looks like now that I'm done with it (though, I might add a tow bar for my kayaks). Even with the added weight of the rack, fenders, 12V headlight and battery pack, and oak block pedals, it's only about 35 lbs.
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