I have connected my Retro-bit console
When playing something like Super Mario it is visible on the overworld screen, when looking at the edges around non moving sprites it have some vibration..When playing a level it also visible on the white clouds..

Did see the shaking/vibration on the green edge around the water by the castle and on the white text on the bottom hud.
Also tried Lion king on Sega, but the shaking/vibration was very visible on the white/light background when the first level starts:
https://youtu.be/1Kc5jPdfHLY?t=19
Did not really see anything on the actual sprites when I did the test.
You are talking about 50Hz, but I'm in europe, so is this still a problem?
Have not used an CRT for like 10-15 years, so I may just forgotten how "bad" the image was..