Differences between these translations below and the existing ones include:
* changed order of string "fpsreducer.key.openGui" and "key.categories.FpsReducer"
* changed option description "FPS Reducer" to "Reduce FPS during inactivity" to make it clear that this is a separate option and turning it off doesn't affect other FPS reducing options, like e.g. "fpsreducer.config.menu.reducingInBackground"
* changed "Detect moving" to "Detect Movement", because it sounds more professional, or so
* changed "Reduce FPS when inactive" to "Reduce FPS when in background" to make it clearer what word "inactive" meant; "in background" can mean "not in foreground", which is caused by just not having Minecraft window focused; "Reduce FPS when game is in background" would be better description, but having this, due to the lack of available space, is impossible
* changed "Suppress sound when inactive" to
"Suppress sound when in backgr." "Suppress sound when in background" for the same reason as above; "Suppress sounds when game is in background" would be better description, but it is also impossible ; I even had to shorten word "background" here to don't let it exceed button width with the default Minecraft font
* removed hyphens from "top-left", "top-right", etc. and made the first letters uppercase to be consistent with strings "fpsreducer.config.menu.detectMoving"
* changed "Idle FPS" to
"FPS limit in eco mode" "Max FPS in eco mode" to, again, make it clearer what word "idle" meant, it could mean "without user interaction", and it is true, but not completely, because this config option also covers scenario in which the Minecraft window is not focused and a user is interacting with e.g. inventory slots by moving cursor over them, but not clicking them. Additionally, if a user set this option on a value higher than their computer is able to provide (e.g. set: 30 fps, real: ~20 fps), this option will not make magically they reach the specified value, so word "max" here makes it even more clear, what this option do.
Additionally, I noticed that the following strings are unused: "fpsreducer.config.menu.suppressedVolume", "fpsreducer.config.menu.waitingTimeMin" and "fpsreducer.config.menu.waitingTimeSec". Maybe consider removing them if you are not planning to use them in the near future.
Here you can get slightly improved U.S. English translation JSON file for FPS Reducer mod for Minecraft 1.14.4:
And here you can get slightly improved U.S. English translation text file for FPS Reducer mod for Minecraft 1.12.2:
EDIT: I updated the links above, because I set them to expire in 30 days and now the time is over. And since I know that you will increase the buttons width, I replaced the shortened word "background" with its normal form.
EDIT2: I slightly updated the translations for both file formats (more specifically I changed "FPS limit in eco mode" to "Max FPS in eco mode"), so also the links.