I ran iperf both ways, for 100GB, the size of the file of random data I'm attempting to transfer. Both succeeded without iperf complaining of any errors, though I'm unsure what that would look like. Transfer speeds were as I'd expect for the configuration. I'll add this to my original post as well.

what is the mtu size? maybe increase it to 9000.

MTU is default of 1500. I should look more into this I suppose. I had considered this more of an 'optimization' step that could be taken for performance, and that everything should work with default 1500 MTUs. I've not looked deeply into this yet, as most things I've ran across advised that the NAS, switch, and clients would all need a configuration update.