I have this set up on a MTB with 819s, so ca. 35 psi, and found a generic inner tube lockring wasn’t good enough (although maybe it would have worked given time if the sealant solidified around the valve). Needed to use some old UST lockrings I had lying around, which have been v reliable.
90-100 psi sounds like a totally different story, though – no experience with road tubeless. What tyre are you using on an 819 at 90 psi?
Mavic valves do work fine, but they are prone to corroding onto the rim over time. Few posts on here about folk stranded in the hills after a UST puncture and no way to get the valve out. Worth unscrewing the lockring and retightening once in a while to make sure this doesn’t happen.