I would strongly suggest not using 900GB 10kRPM drives (and especially not 10 of them) in [current year] when brand-new 8TB hard drives cost $120, and 14+TB recertified drives aren't much more than that. The power costs of 7 more drives than you need for the capacity definitely add up over several years of runtime.
OpenWRT, because it has a nice interface, runs on half a toaster, and I've yet to find something that I need it do that it couldn't do but OPNSense could.
I did try PFSense many years back and it just seemed overly complicated and generally flaky. I had trouble setting it up as tinc vpn client despite that being a trivial task in OpenWRT, so I switched back.
I would strongly suggest not using 900GB 10kRPM drives (and especially not 10 of them) in [current year] when brand-new 8TB hard drives cost $120, and 14+TB recertified drives aren't much more than that. The power costs of 7 more drives than you need for the capacity definitely add up over several years of runtime.