Hi, I'm not using it for a ring light myself, however so long as what it connects to is strong then there would be no problems.
The whole Elgato mounting system is both solid and easy to adjust. Placing a Elgato Key Light on the L mount is no problem so the ring light should be ok.

I am 99% sure that it can yes. Would not make sense for them to use a different threadding. and visually it looks the same.