I've had this issue as well and have had no luck with the above suggestions..
To be more precise, I was experiencing a lot of micro stutters after being in the game for a while..
What seems to have alleviated the issue for me is to disable full screen GPU driver mode!!
Note that g-sync is working fine even if set to run on fullscreen only..
I will be testing this further since I've only tried it for about an hour, but it would help reach a conclusion if others can test this as well..
My specs: 14700KF, Asus 4070 TUF, 32GB DDR5, and a 180Hz G-SYNC 2K monitor."
I also tried backing up the configs folder bellow and reinstalling..
Before doing so make sure you export the controls in game and taking note of your graphics settings..
Rename the configs folder bellow to keep old settings just in case and reinstall..
C:\Users\<USERNAME>\Saved Games\DCS
..\DCS\Config | Holds most config including game options, servers, passwords and more..
..\DCS\Config\Input | Contains in-game control settings..
..\DCS\InputUserProfiles | Contains your saved control profiles..
Other folders are self explanatory..
This is what made the biggest difference for me but disabling fullscreen also helped as well..
Had a few spikes today as well in MP but not in the same occurrence rate..