How to set up 2 PCs with 2 wired connections for Internet and LAN usage?

Question

I have 2 Windows 10 PCs (Home edition), and I'm trying to set up a home NAS server, as shown below. I use my 2 PCs for gaming and streaming (respectively).

I have a Gigabit router, 2 USB to Gigabit Ethernet Adapters, and an Un-managed Gigabit Network switch, which connects the 2 PCs, in 2 distinct paths. So, both PCs have 2 Ethernet adapters each, and I have set static IPs for all 4 adapters. The static IPs for the Internet-facing Router are of the form 192.168.0.xxx and the IPs for the LAN-facing Switch are of the form 192.168.2.xxx (No specific reason to do this, I just wanted to easily be able to identify which network I'm dealing with just by looking at the IPs).

My goal is to make sure that my gaming and streaming are not affected by the local NAS file transfers, and also to make sure that the NAS file transfers use the full Gigabit bandwidth (I know it won't hit the theoretical maximum, but that's fine). I want to make sure that all bytes related to gaming/streaming only use the Router (192.168.0.xxx adapters) and all bytes related to NAS file transfers only use the Switch (192.168.2.xxx adapters).

I was able to establish connectivity, but I do have a few questions about this setup, could someone please help me with these?

1. Is this the correct way to set up the PCs, for what I want to do? Most websites talk about connecting multiple PCs to the switch, and then connect the switch to the router. But my goal was NOT to share the internet connection, I just wanted a dedicated network for NAS transfers, and a dedicated network for Internet access.

2. I had to set both Private and Public profile in the File and Printer Sharing Inbound Rule in Windows Firewall, without it, I wasn't able to connect to the 2nd PC using the 192.168.2.xxx IP. Is it safe to use Public profile? I have read that it should ideally only be Private profile?

3. I initially thought that I would get close to 1 Gbps bandwidth each on both networks, but when I ran 2 simultaneous iperf tests, I only got close to 1 Gbps in total. Based on the blinking LEDs, I'm confident that only the Router was used when I used 192.168.0.xxx in the iperf command, and that only the Switch was used when I used 192.168.2.xxx in the iperf command. Since they are technically 2 separate Gigabit networks, shouldn't I have got close to 1 Gbps speed on both networks, independently? Right now, speed is effectively being halved on both networks. There is no issue with either network, I'm able to hit Gigabit speeds when I run single iperf tests on either network, so the halving of speed is happening only when I run both iperf tests.

                   Internet
                      |
                      |
                 Gigabit Router
                      |
      (192.168.0.xxx) | (192.168.0.xxx)
    __________________|__________________
    |                                    |
    |                                    |
Windows PC 1                         Windows PC 2
    |                                    |
    | (192.168.2.xxx)                    | (192.168.2.xxx)
    |                                    |
USB to Gigabit                     USB to Gigabit
  Ethernet                            Ethernet
  Adapter                             Adapter
    |                                    |
    |____________________________________|
                      |
                      |
                  Un-managed
                   Gigabit
                   Network
                   Switch

Screenshot of the above

Answer 1

May I ask why you don't connect the PC1, PC2, & NAS to gigabit router? If it doesn't have enough ports connect the unmanaged switch to gigabit router then connect whichever devices to that? I honestly believe you are needlessly complicating it, but I'm guessing you may be doing it because you're worried the NAS or services to NAS may somehow affect your internet speed? How I handle this at home is a $50 firewall (Ubiquiti EdgeRouter X, but many others could work) blocks outbound WAN access to NAS. Mine is mostly regarding security, don't want it phoning home; however it has the same result of it not affecting my internet speed since it literally cannot get to it

---

--EDIT

1. If its working it clearly is A WAY to do it. You confirmed via a comment that while utilizing NAS it clogs your pipeline to the internet. Based on your comment wording I'm speculating the router is overloaded while using NAS & trying to pipe internet.

   a. Another option: Instead of unmanaged switch for NAS network, use an old router

   b. Another option: Don't use static IP, try using the PC's self-assigned IP (169.254.x.x called APIPA)

   c. Another option: Buy a better main router

2. It is safe to use Public, Windows automatically sets new networks to Public unless you change (to Private). Public is the most restrictive/safe by default. Private allows the most. Each can be customized to open more ports so Public COULD be the most dangerous if you've tweaked it a bunch.

3. This is the award winning question. Since you can hit 1Gbps on each network separately process of elimination SEEMS to deem the network & USB adapters not at fault. So now I'd start looking at the PC as the common denominator. Watch task manager to see if its using a ton of CPU or RAM. Use your more powerful PC to test. It could be something with the TCP/IP network stack too of which I don't have an answer myself.