static routing for nas on wds setup

Your network will only be as fast as the slowest component. So if you are using a wireless connection, then that will limit performance accordingly.

And you may have other problems as well. For example if both routers are providing IP addresses there will be confusion on the network. Only one router should be providing IP addresses.

Are you in a situation where there is the need for a wireless connection between the two routers? I.e., there is no apparent way to run an ethernet cable from the location of the 1st router to where you have placed the second router.

You may be able to use Powerline adapter instead. Is that viable?

I didn't watch the full video, but the diagram at 7:40 makes it look like your 1st router is the main router, and your 2nd router is just acting as a WiFi bridge (i.e. the gateway on your PC and NAS is still the 1st router). In that case, sometimes info transferred between your PC and NAS (connected to the 2nd router) will be sent via the gateway (1st router).

It's also possible using the 2nd router in this way sets it up as a dumb bridge, where all traffic it gets over its LAN ports is reflected over WiFi to the gateway. Which would slow it down to WiFi speeds.

I see two easy ways to fix this.

- Buy a switch. Connect the PC and NAS to the switch, plug the switch into the 2nd router. The switch will realize the traffic between the PC and NAS can occur entirely within the switch, and "won't bother telling" the 2nd router of the data transfer. So it should transfer at the full speed of the switch.

- Or reconfigure your network so the 2nd router is a WiFi client, not a bridge. I'm not sure if the WR841N supports this mode (looks like TPLink calls it AP client mode). In this mode, the WR841N acts like a router, getting Internet via WiFi instead of its WAN port (the WAN port is unused) This will cause its LAN ports to retain their switch-like abilities, including not automatically forwarding all LAN traffic to WiFi. The downside of this is that the 1st and 2nd router will be separate networks. Devices connected to the two will have different IP address ranges and gateways. Devices on the 2nd router can see devices on the 1st router (just like they can see the Internet). But devices on the 1st router cannot see devices on the 2nd router (they're protected by the 2nd router's firewall).

https://www.tp-link.com/ch/faq-442.html

Edit: Also be warned that I believe the WAN port on the WR841N is only 100 Mbps. Not really a big deal if you're connecting it to the Internet via WiFi. But in the event that you ever use its WAN port and your get Internet service faster than 100 Mbps, it will not be able to give full Internet speed to devices connected to it.