Welcome back from your surgery. I hope you're feeling well. <img src="https://www.ubbcentral.com/boards/images/graemlins/smile.gif" alt="" />
Bob, I don't recall the name of any photography forums that recently moved to Threads... could you provide a link? Their issues sound quite odd, and are certainly not the norm!
The default installation of MySQL comes with a handful of recommended configurations suitable for different server and load configurations. Usually it's best to start with one of those, and perform tweaking as needed.
MySQL tweaking is not a Threads-specific thing. It has to be done with any major application. As I noted above, there are a number of general rules and guidelines that can be followed. As we get closer to the beta period, I'm sure that we'll be posting tips and tricks.