If it helps, have a look at my sVDEV resource page. I have a number of planning steps, results, and so on. For my use case, it has been an incredible improvement as the write speeds nearly doubled between optimizing the record sizes for larger files, turning on zstd compression, and using sVDEV to leverage SSDs for small files and metadata. (thanks @winnielinnie !)
Another hidden gem WRT to sVDEV is being able to designate specific datasets to solely reside in the sVDEV by setting the dataset recordsize to be equal or smaller than the sVDEV recordsize cutoff. So you can have your cake associated with mirrored SSDs for databases, VMs, etc. and eat it too, by also using them for metadata and small files.