For most of my bike commuting life, I've had a hybrid or hardtail mountain bike. As I got older, I added rack & fenders. (I don't like a sweaty back)
I have two commuter bikes now:
- Trek Verve 3; it's their comfort hybrid. It's from about 7 years ago; when they still had rim brakes. I added Planet Bike fenders and the Bontrager rack. It has a cheap Amazon trunk bag, a tube top bag and a set of lights. It's great. The 45 mm tires are meaty enough and it has a little shock in the seatpost. Only problem with this bike is that it's slow. I find myself averaging 12-13 mph on it where I would average 15 mph on my road bike.
- Aventon Level.2 (eBike) - This is the perfect commuter bike. The lights are built-in and the rears serve as brake lights too. In addition to the one on the rear fender, it also has a pair of lights in the seatstays. I replaced the stock rack with a Topeak MTX rack and I have their expandable trunk bag with fold-down panniers. It's a Class 3 eBike, so I unlocked it to allow 28 mph under pedal assist. (20 with throttle) I'd say I use it about 30% unpowered, 60% on the lowest level of assist and 10% at higher assist levels when I need to make time. At the lowest assist level, 15-18 mph on flat ground is pretty easy; won't sweat until it gets above 75 °F. When it gets warmer, I can dial in assist level 2 or 3. When it's cooler, I often turn off the assist to make a bit more of my own heat. (Here's a link to my long-term, unsponsored review on it)
I'm thinking of buying another bike in the future that could serve as a nice middle ground between the above two: a steel-framed gravel bike. Why?
- Drop bars are better in traffic (narrower) AND more aerodynamic. The only time I miss the leverage of flat bars is on rough trails, which I don't ride much of, these days.
- Meatier tires than a road bike handle bad roads better
- Faster than a hybrid or mountain bike
- They usually have provisions for rack & fenders
Last option would be an endurance road bike, like my Trek Domane AL3. It is a road bike, but built for comfort and a wide range of usefulness. With its stock 32 mm tires, it rolls smoothly, but they're still wide enough to give a good ride. (regardless of frame material) With those stock tires, it can accommodate fenders. Without fenders, it can accommodate up to
38 mm 35 mm tires.
The thing about a fast bike is that it's never a detriment, unless you go too skinny and hard on the tires. Don't want to go as fast? Fine, but you'll still be faster than a less efficient bike with the same effort. Or go slower with almost zero effort, on those really hot days.