Do you even get no stuttering with company-minimum-prefix-length set to 1 and company-idle-delay 0? I tried building --with-json, and `(json-available-p)` returns `t`, but it's still super stuttery.
I have the exact same settings on those specific variables. I do not experience any stuttering at all.
I am on a pretty powerful system though, I have a Ryzen 3900x and 32GB RAM which may be why I am not effected by this. I also have the garbage collection settings tweaked a bit. I am on version 29 for comparison.