Quick question... I want to hardware encode 2 streams. If the 2nd stream has Use Stream 1 Quality checked, will it also use hardware encoding? The hardware encoding option for Stream 1 is greyed out unless I uncheck Use Stream 1 Quality, which is why I'm unsure what option to use to ensure both streams are hardware encoded.

To clarify, yes ticking that box will also copy the Use Hardware Encoder setting, so be sure your GPU has enough encoder channels available. (2 for GeForce, no fixed limit for most mid-high end Qusdro models)

With the three streams being independent since vMix 21, are they not all encoded separately even with "Use stream 1 quality" selected?

Usually streams with the same settings to multiple destinations are only encoded once and pushed to the destinations. But this does not allow independent start and stop by default.
However depending how Martin wrote the independent stream feature 2 options are possible:
- each destination has a dedicated command line for FFMPEG, even if encoding parameters are the same
- streams sharing the same settings are encoded just once, only the destinations part of the command line is "dynamic" and can be updated on the fly

Only Martin knows I'm afraid... unless the stream logs contains clues, I never thought to check this...

Thanks Richard, Guillaume and Martin for clarifying.

Independent streams is the single biggest improvement for us in vMix 21.

I just replaced a GTX 1060 with a Quadro P2000, so the resource cost for additional streams is very limited with hardware encoding enabled for both recordings and all three streams. Makes me wonder whether we didn't do this before as the price premium is almost negligible.

It's not possible to say a number as it will allow as many simultaneous encodes as possible depending on the actual load of the card. So it will vary according to what's the card's used for at the same moment.

Guillaume