Hello Billy .... yes, both of the functions you suggest are true for the most part. The heating elements will likely last longer operating at lower temperatures, and the water boils softer as well, so that you can control the engine speed to a certain degree, especially helpful on engines without steam line throttles.
Another alternative is a device marketed as a router speed control. They are good for up to about 15 amps / 1800 watts and are found from various sources at around the $20 mark. Harbor Freight sells them for a bit more than that, as seen here:
https://www.harborfreight.com/router-speed-control-43060.html ... but often has sales that brings the price down quite a bit. If you look around you'll likely find others at sale prices as well.
These units are good enough for most electric fired steam engines with only a single heating element, but some of the larger engines, like Gil often runs, have more than one, so these little units may not be enough.
I like them, and use them at least as much as my Big Red Variac.
Hope this helps.