Dolphin runs like an absolute charm on my PG279Q with G-Sync. That's a 144 Hz display, though. Are you running a 60 Hz panel, by chance? Just a complete stab in the dark, but I wouldn't be surprised if lower-refresh G-Sync/FreeSync monitors can cause timing issues in emulators that wind up looking like framerate drops.
You should see how things behave when you disengage G-Sync when your framerate exceeds your refresh rate.
You should see how things behave when you disengage G-Sync when your framerate exceeds your refresh rate.
Quote:To use this new mode, set “Vertical sync” to “Off” on a global or per-game basis in the “Manage 3D settings” section of the NVIDIA Control Panel. When your frame rate exceeds your monitor’s rated G-SYNC refresh rate, for example 144Hz, G-SYNC will be disabled.