Exactly what I was looking for, it has text outline option called "stroke". Very helpful because default subtitles blend with a video, even changing color doesn't help.

EDIT:
After having the extension OFF the whole night it suddenly started working right when I turned it on.
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love this but suddenly the font and size option gets ignored. the default gets overridden

It's good enough. I hope it gets applied to shorts too.

非常棒，這就是我想要的字幕加強套件！