Canon M6 II with a speedbooster and a Canon EOS R: a great youtuber FF video combo?

How good is the Canon M6 mark II with the Viltrox speedbooster (focal reducer) as a B cam to the Canon EOS R?
Is this the best affordable youtuber full frame film making combo?
How much field of view and bokeh does the speedbooster gives you over the standard APS-C crop?
I'll use photography and video to compare crop, bokeh and detail.
Music:

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Видео Canon M6 II with a speedbooster and a Canon EOS R: a great youtuber FF video combo? канала Islander