Important to my B&H loaner support — buy your Sony A1 via links on this site.
Roy P writes that Sony says:
Thank you for contacting us today and your interest in our new camera.
The Sony A1 uses the same battery, same battery grip as the Sony A9 II (VGC4EM) and no change to the Mi shoe with the exception that it can accept digital signal from our microphone ECMB1M.
DIGLLOYD: this means that the $88 Vello BG-S7 can save you a bunch of money vs the $398 Sony VG-C4EM. If all you want is a lot of battery power, that’s a deal!
Personally, I greatly prefer carrying just one or two extra batteries with me as the battery lasts a long time. But some uses really do need a lot more battery power in one go.
The Sony A1 has dual card slots and can use either CFExpress or SDXC.