Anyone with hands can buy an e-bike kit with a hub motor and install it on a bike they already have.
Hub motors are relatively simple motors and are completely self-contained. This means you can use an off-the-shelf one on almost any bike, and if you upgrade your bike, you can transfer it from one bike to another
crank drive motor
Installing a crank drive motor is a highly skilled job, and few people would buy one and install it on an existing bike. Most commonly, the crank drive motor is part of the original manufacture of the e-bike.
Advantages and disadvantages of hub motors and crank drive motors in terms of ride feel
Hub motors and mid-drive motors
Hub motors basically propel you forward from behind through the rear wheels. In contrast, the crank motor is almost integrated with your pedals. Because of this, many experienced cyclists say that e-bikes with crank-driven motors offer a more natural ride.
On the other hand, if your main concern is traffic, feeling may not be your primary concern.
Pros and Cons of Hub Motors vs. Crank Drive Motors for Engine Heating
The hub motors are completely sealed. This means that there could theoretically be an overheating problem since the heat is not easily lost. However, most units have a controller to monitor and control it. With a quality bike from a reputable manufacturer, you should have no overheating issues. In the years of using hub motors, I've never had a problem with overheating.
Crank drive motors usually have a scalloped housing, which dissipates heat more efficiently than hub motors.