

In the context of communication networks, WiFi is a high speed netowrk. It was designed to be basically a “normal” (ethernet-like) network, but wireless. It acts for all intents and purposes like an ethernet network. There are significant requirements that devices need to follow, many include frequently saying “hello” (simplified). The complexity of the protocol to be able to send at gigabit and faster speeds over dozens of meters is significant. Having relatively low latency adds to this as well. If all you need is a few bytes every now and then, that isn’t ideal. Having devices in your network that follow older/slower standards is essentially like pulling the handbrake for your network (again, very simplified). But explaining this in detail is also very much beyond the scope of a comment here.
ZFS, specifically RaidZx, can be expanded like and raid 5/6 these days, assuming support from the distro (works with TrueNAS for example). The patches for this have been merged years ago now. Expanding any other array (like a striped mirror) is even simpler and is done by adding VDevs.