Is there any benefit from joining the windows insider program?
Well, for me, it was to check compatibility of some software. For example: Sandboxie. For me, the usability for browsers with this software took a sharp downtown in v. 2004. So, I took this info and made alternative security arrangements.
Of course, I also like to check how performance is ( I found it to be comparable to 1909) as well as certain bugs, how they would (or would not) be handled with successive updates.
Fast Ring is definitely riskier. For example: one time, I was stuck in Safe Mode after a run w/DDU and could not escape at all. This caused me to have to revert to 1909 again. Expect the unexpected w/Insiders, for sure.