Shooting 4K all day on GH5 - settings and SD card suggestions

I shoot weddings on the GH5. I shoot in VLOG, and normally shoot the following

• wide angle for ceremony and speeches in 4K 10bit 25fps
• all other handheld 1080p 10bit 50fps

I want to start shooting everything 4K, so I can have more flexibility with cropping in etc.

I heard 8bit was bad for VLOG, but it’s the only 4K option on my camera that also does 50fps, which I need as I speed ramp and slow down footage a lot in my edits. Is this a viable option?

I have also run into some issues lately with card reading. What’s the best cards for reading a lot of 4K footage. Does it have to be 300mbs?

Thanks in advance