Ext4 is gonna be the fastest for general daily use. The extra utility of copy on write filesystems is stuff like efficient snapshot backups, optional compression at rest for your files, and really really fast copy operations.
AMD's drivers are fully FOSS and built into Mesa, whereas Nvidia's are closed source, so yes, AMD GPUs are more reliable and less of a hassle on Linux. However, Mint makes dealing with Nvidia drivers easy, so it's honestly your call there.