Sony A7rV Preorders:
In US at BHphoto, Amazon, Adorama, FocusCamera, BeachCamera, Buydig.
In EU at Fotokoch, Amazon EU, FotoErhardt, Calumet DE, WexUK. ParkCameras UK.
In Australia at CameraPro, Camerahouse, Sony.
A full Sony A7R V vs Sony A7R IV vs Canon R5 vs Nikon Z7 II spec comparison can be seen on that special BHphoto page.
And here is the comparison between Sony cameras (Click on it to enlarge the image):
