Vivaldi Helper Requires High Performance GPU
I just noticed by way of the excellent gfxCardStatus program, that Vivaldi is forcing my MacBook Pro to use its power-hungry discrete GPU instead of the energy saving integrated Intel GPU.
Activity Monitor shows that the process "Vivaldi Helper" requires a high performance GPU. This doesn't seem like it should be the case and is probably a bug.
Vivaldi should probably also support App Nap (which can further reduce power consumption) like Chrome and Safari are able to.
Hmm, try and untick the chrome setting "use hardware acceleration when available" and see what happens.
You can get there by visiting chrome://settings/ and clicking "show advanced settings". This will of course disable all hardware acceleration, at which point your cpu does the job....
... and don't forget that the change won't take effect until you restart Vivaldi. When you do, go into "Tools / Task Manager" and you'll see that the GPU Process helper is no longer active.
FYI, here's what's going on in that GPU Process:
Chromium-based browsers use the GPU to accelerate compositing and it's (typically) more efficient and better in terms of performance than using the CPU because the GPU is designed for these types of workloads. You'll have to profile your system to see if disabling hardware acceleration really gives you a net benefit.
One more thing... vivaldi://gpu will give you some additional information should you try switching to the integrated GPU and compare its capabilities to the discrete GPU.
While I don't dispute the point you were trying to make in your initial post, I don't think that using the discrete GPU is a bug given that it's available for use. Some features might not be available on the integrated GPU either (arguably) making the discrete GPU a better choice.
Best of luck with your testing.