Extending the WiFi at home

At our home we have a TP-Link AX4400 router located in the upstairs guest bedroom closet. However, the router doesn’t cover the first floor far corners where we have another bedroom for my brother who struggles with WiFi connection. There is an Ethernet cable going through the wall and into the first floor to my computer.

My plan is to buy a second router and connect it via that Ethernet cable in my room, that way there is a router upstairs and downstairs, and then just plug my computer into the new router so I still have a wired connection. However I’m unsure if this can actually work. I saw that TP-Link devices have something called OneMesh, which on paper sounds ideal for having the same signal across the house, but I’m unsure how this truly works.

Should I he going down this route of getting another router and linking them together with that cable? If so what other information do I need to set it up. Is this one mesh option what I need?