I have a water-cooled 1.5kW spindle. I have a CW-3000 clone cooler that leaked and is noisy. In retrospect if I were doing it over from scratch I’d have used a CPU cooler. It doesn’t take much cooling, honestly. And @Eclsnowman used a CPU cooler on his LienCNC V2 with a 2.2kW spindle cutting aluminum. I would expect any of the commercial units to get this right out of the box; it is those of us designing our own that get into trouble here. 
Air cooled spindles typically have a fan attached to the spindle axis that just blows air over the spindle. Some are exposed (my previous 800W spindle brushed spindle had an exposed fan that ate through my vacuum hose when it touched), and some are protected (typical when the spindle is presented in a rectangular case like this Vevor).
For half-inch shanks, ER20 is as small as you can go. It will be the sweet spot for you. ER collets each have a range of supported shaft diameters, so if you have a full set of collets you can hold basically any tool within the total range.
Those three units and the Camaster Stinger I look generally comparable.