Depends on the network speed. At 1Gbps a single HDD can easily saturate the network with sequential reads. A pair of HDD could do the same at 2.5Gbps. At 10Gbps or more, you would definitely see the benefits of caching in memory.

Makes sense. I didn't know if the FS used RAM for this purpose without some specialized software. PikachuEXE and Mewse mentioned ZFS. Looks like it has native support for caching frequent reads [0]. Good to know

[0]: https://www.truenas.com/docs/references/l2arc/