You might try adding a cache drive instead. It can help lessen the memory usage zfs needs to maintain speed. My server is spinning rust with an ssd drive attached to the pool as cache.
Command would be “zpool add pool_name cache /dev/sdX” where pool_name is the pool you want the cache on, and /dev/sdX is the empty drive you want to use with it (or partition). Make sure to encrypt this drive before setting this up, my knowledge is zfs doesn’t do that for you.