Eos R7: EF-EOS R 0,71X, Viltrox 0.71x EF-R3 or Metabones Speed Booster?

EOS R7 should be able to use most/all EF lenses with Canon EF-EOS R 0,71X adapter, the Viltrox 0.71x EF-R3 or Metabones Speed Booster, to heavily reduce the crop (1.14X) and gain 1 stop of light, which one is going to be better with AF, resolution, compatibility, IS working properly, etc ...?

Rudy Winston, from Canon, confirmed in an interview that Canon EF-EOS R 0,71X adapter will not break the camera or the lens, but (unfortunately) there is no official support, so probably no in camera lens corrections and maybe other issues, or maybe it will still work flawlessly, but without the official support deserved only to Super 35 EOS Cinema cameras.

Viltrox 0.71x EF-R3 should work, maybe after a firmware update, same for Metabones Speed Boosters, but which one works better with EOS R7 should be tested.

In the future theoretically, Viltrox, Metabones or someone else (even Canon!) could even cratere also an RF to RF speed booster (with a different optical formula) as it's "just" a reversed extender and extenders are popular , speed boosters deserve to become popular too, once good APS-C cameras are available.

Now that it's confirmed that Canon continues the 1.6x crop  with the RF mount, even a proper 0.63x booster can/should me made to gain back an equivalent 1x FF (Metabones already makes something similar for M4/3, the 0.64x and 0.58x) I know it's wishful thinking, but with the R7 at this price, I'm guessing most Canon APS-C DSLR photographers will migrate to the R7 or R10 soon and millions of perfectly working EF lenses are not going anywhere, so there is a huge market for EF to RF Speed Bosters/ Focal Reducers, as I'm guessing the R7 (and R10) will be much more popular than the more expensive FF RF mount cameras.

Any early R7 adopters had the opportunity to use the existing 0.71 x adapters and see how good or bad are with their new camera?