I am not at all an expert, I can only share my anecdotal unscientific observations!

I'm running a TrueNAS box with 3x cheap shucked Seagate drives.*

The TrueNAS box has 48GB RAM, is using ZFS and is sharing the drives as a Time Machine destination to a couple of Macs in my office.

I can un-confidently say that it feels like the fastest TM device I've ever used!

TrueNAS with ZFS feels faster than Open Media Vault(OMV) did on the same hardware.

I originally setup OMV on this old gaming PC, as OMV is easy. OMV was reliable, but felt slow compared to how I remembered TrueNAS and ZFS feeling the last time I setup a NAS.

So I scrubbed OMV and installed TrueNAS, and purely based on seat-of-pants metrics, ZFS felt faster.

And I can confirm that it soaks up most of the 48GB of RAM!

TrueNAS reports ZFS Cache currently at 36.4 GiB.

I dont know why or how it works, and it's only a Time Machine destination, but there we are those are my metrics and that's what I know LOL

* I don't recommend this. They seem unreliable and report errors all the time. But it's just what I had sitting around :-) I'd hoped by now to be able to afford to stick 3x 4TB/8TB SSDs of some sort in the case, but prices are tracking up on SSDs...