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for random IO you shouldn't use raidz1 or worse raidz2. use mirrored vdev. there're already multiple answers to this in the forum - just search it.
if you want to improve sequential IO throughput you could use raidz1 but this of course depends on your IOPS workload.

I would start without L2ARC - https://forum.proxmox.com/threads/zfs-worth-it-tuning-tips.45262/post-217209

SLOG will only help if you don't have async IO - check before adding it

and of course only HBA's.