Optimus, vsync and performance seems to be a topic that continues to be problematic for a lot of people (including us, I should add!). So I went and got myself a laptop with Optimus and a Nvidia GTX 1070 for testing. Trying out different settings, I came up with some interesting results.
These tests are all done on a Win 10 laptop, using the recommended updates for Windows (Fall Creator) and Nvidia (driver 390.77). 3 connected displays running at 1920x1200 each. The vsync is controlled by the 'Vertical sync' option in Nvidia Control Panel, set for Arena.exe. All other settings and Global Settings are left at default. Optimus is controlled by enabling or disabling it in BIOS. I tested for tearing and judder with a horizontally scrolling Lines source in a 5760x1200 comp. The Lines source was colored pink because I'm a real man.
Optimus enabled, vsync set to 'Use 3d application settings': 20 fps, no tearing
Optimus enabled, vsync set to 'On', 15 fps, no tearing
Optimus enabled, vsync set to 'Off', 140 fps, with considerable tearing and extreme judder.
Optimus *disabled*, vsync set to 'Use 3d application settings': 60 fps, no tearing
So it looks like having both Optimus and vsync enabled somehow reduces the framerate with each connected monitor. Disabling Optimus lets Nvidia do its thing and everything is as expected.
Now here's the interesting one:
Optimus *enabled*, vsync set to 'Off', Composition Framerate
in Resolume set to 60. Result: 60 fps, no tearing.
This was a surprise to me. Apparently, our new framerate cap is tight enough to force correct monitor refresh updates, even when vsync is disabled and Optimus is running.
Now if you're using the laptop strictly for shows, I'd probably turn off Optimus completely. Saving the battery is pretty pointless then anyway. But if you want to save battery life, going into BIOS sounds really scary, or can't turn off Optimus in BIOS at all (which apparently is a thing on some laptops), turning off vsync and letting Resolume handle it, seems to be a very viable option.
Note that this is the result of a single morning of testing, not an endorsement of anything or an end-all advice on how to do things, valid forever. Graphic drivers are a nightmare to work with, and your mileage may vary considerably.