Camera Cards for Wallet Backups

UPDATE: as it turns out, using an APFS encrypted volume on SDXC cards is just too slow (around 34MB/sec), no matter the card reader. As I am no longer willing to take the risk of unencrypted data in a wallet backup, that means switching to CFExpress Type B cards, which offer outstanding performance with APFS encryption. See the encryption discussion at bottom.
This post has been moved to MacPerformanceGuide.com