[Plugin: Safe Function Call] Does it use 'echo' or '_e'?

It uses echo. _e() is only really useful if it is utilized in conjunction with a textdomain, which can’t be parameterized.

It technically adds a slight bit more overhead. It essentially does the condition checks you’d do, but in order to accommodate passing along arbitrary arguments (making it flexible), it also uses func_get_args(). The extra overhead is quite minuscule and shouldn’t be noticeable. Even if being done 25+ times in a page.

With the plugin, you save in time writing the code, you write/see less code, and have some flexibility afforded by some of the various methods provided by the plugin. But everyone’s perception of that value will vary.