Hello,
I want to thank you for posting this. I was having the exact same stuttering problem and it started only yesterday. I'm not sure why it just suddenly started shuddering but I played DCS for about a week since getting my new NZXT pc with a 4090 with out any problems, and then suddenly for some unknown reason this stutter started to happen.
Disabling the power service did in fact take care of my issue. I'm pretty sure I attempted to reduce all power saving features during my initial windows install and setup.