Here's my analysis on a bunch of @ZabuJard's older videos.
Works
When health is at 100, the last digit cuts off partially
Blur effects don't work.
Health set to 100 in the screen with the giant eyeball, but returns to normal in the next screen
Fully playable, but includes many blur effects not supported, such as projectiles or clouds in the background.
Time variable uses the wrong font.
As far as I got, nothing too noticeable.
Just a common preloader issue. Couldn't find any more differences, because I can't access the original Flash once it's in Ruffle.
Video playback issue.
Currently running on Ruffle albeit not perfectly. Luckily, I downloaded it before Ruffle was implemented, so I can report certain issues.
Blur effects in the surgery room scene, the shading in the raindrop room scene, and more, aren't visible.
Video playback in the spider channel issue
And there's more that I didn't have time to look through. I really need a way to run flashes in the Newgrounds Player after Ruffle is turned on, so that I can make a better comparison and ensure that no mistakes are left unnoticed.