It likely won't make any noticable difference. But compare the energy impact in Activity Monitor (just make sure to close the BTT preference window while doing so or it will seem really high).
Also, I know you said it doesn't need to be actionable, but it is possible to make it so that pressing the button rotates between languages, or you can make a group with buttons for each language you use and set them to switch to that language when pressed. Like this:
Let me know if you want either of those options and I'll give you the script.