I would recommend doing more than gaussian blurring. Blurring makes it harder but not impossible to recover, especially if you know the exact font and font size in an image (which is easily recovered when the attacker can visit the website to work it out!).
https://youtu.be/acKYYwcxpGk here's a citation for that being possible, in case anyone's interested. Also has some of the methods posted on github from what I remember.
Yep: https://github.com/bishopfox/unredacter
We would need actual black bars.
Or if you want it to look "authentic" replaced it with blurred random text.
But personally I like solid bars as it makes it obvious what is happening and that it is secure.