ja3h, for what you want it for I would perhaps look for a tourer.
Shopping (panniers) Much comfy and safer than backpack
10 mile distance (want something nippy/not so much drag) Thinner tyres than MTB, more crouched position. Drop bars to change hand position. With flats you're stuck in a single position - unless you get bar ends, so if your hands are sore a quick position change solves it.
Slight off-road- not so thin. 35-38.
Mudguards, all-year/weather use.
Brake levers on the "flats" so you can safetly ride on the flats in traffic, and be able to brake. Road bikes only have brake levers on the hoods.
What do you think of this type of bike?
I wear lycra, it's a lot more comfy than jeans/cotton Tshirt. Lycra shorts with pad for comfort and no rubbing (I went back to underpants and shorts for a day and they're horrible) Imagine a soaking wet pair of underpants plus jeans/cotton shorts.
Lycra only keeps some moisture, so it basically dries straight away whilst you're constantly sweating. A cotton T-Shirt gets soaking wet and will not dry during a ride. tbh once you're out riding lycra looks fine.
This is my bike.
Rode about 1000 miles so far, 36 mile ride is pretty easy, along the flat I cruise 18-22mph.
oh I would also look into clipless pedals, but only once you're really comftable about riding, and riding in traffic. You get a lot more power and control with clipless pedals (pull on the upstroke as well, rather than just down-down-down which tires the same muscles)