I have two monitors, one 120hz+gsync and one 60hz+gsync. I play Tarkov in borderless mode, because that makes it convenient to alt-tab to the other monitor. I'm running a 3080 at 1440p, so I expect to get better than 60fps most of the time.
This works great, most of the time. But sometimes I'll start Tarkov up and all will not be as it should. Things will be stuttering much more than usual, and the game is apparently capped to 60fps. This never happens while playing the game, but it seems to happen after my computer has been asleep or restarted. No in-game setting change, besides switching to full screen, resolves this issue. Restarting the game also does not solve the problem.
Oddly enough, when in this state, the game runs at 120fps when not in focus. But when in focus it runs at 60fps or less.
Fortunately, I've found a way to reliably resolve this issue and get Tarkov back into a working state.
Open the Nvidia Control Panel.
Disable G-Sync and click "Apply".
Enable G-Sync and click "Apply".
After this, Tarkov should be back to operating at >60fps in borderless window mode. Somehow, it seems that gsync is getting confused about which monitor it should be syncing with, or Tarkov is.
I hope this helps someone else who is struggling with this bug.