I used Weller magnastat irons professionally for many years, and I continue to do so at home. The temperature is set by selecting the tip itself, and you change tips if you change the solder you use or the size of the joint you are making.
For general electronics, I recommend an iron with an output of around 45W. Too weak an output can cause more damage since all the wires and components around get heated for longer while you wait for the joint to get hot enough.
Weller are not the cheapest, but they are one of the best, and poor quality stuff is a waste of time. Something like a Weller W61 is good for general electronics; i.e. PCBs and switch terminals etc. RS sell them.