That's the one I've switched to from the "Language Transliteration" add-on. It works pretty good. Wish to see Dark to Light layout switching, as well as a bit bigger fonts for the inline explanations.

Works exactly how I want it. Has an option for a drop down window typing and then copying it where you need to or you an enable the option where you can type using Cyrillic anywhere on a webpage. Simple, effective, private.