Does the max-80%-use target suggested for ZFS for performance reasons apply to SSD-backed pools?
Solution 1:
I'd say yes.
My rule is to stay under 87% on SSD-only pools when using drives that haven't been heavily over-provisioned.
The SSD use case introduces the drive endurance component, while the random write latency is less of an issue that with spinning disks.
Either way, regardless of disk choice, why would you intentionally plan to run your workloads at a high capacity level? All copy-on-write file systems warn/advise against it, so I'd still avoid going that high if it can be avoided.