Idk if Chrome for Mac takes up a lot of RAM but from my experience Chrome indeed drains my 2017 MBP with TouchBar battery faster. Besides, Autocompletion doesn’t work on Chrome. So I stick to Safari to do WK (I can’t live without autocomplete). The thing was my MBP just hung. That’s the first time my Mac hung. I ran WaniKani on all browsers I opened = Safari, Chrome and Opera complete with about 18 user scripts on each browser. Your post made me share this, hence I replied to your post. Right now, I’m WaniKani’ing on Safari only. I’m not sure if running top on my Terminal is a way to know all my browsers take up a lot of RAM though. I don’t feel like testing my Mac until it hangs again.
Have you tried WK Auto Commit User Script? 
Let’s see if you’re happy with no need to press enter.
I wasn’t.