RBR50 coverage for son's computer gaming

Hello!  I purchased the Orbi RBR50 Mesh system 6 years ago (2019).  Router and one satellite.  Router is Firmware v2.7.4.24 and satellite is v2.6.2.4.  I know it's an old unit and I believe firmware updates are  discontinued.  House is ~4400 sf and ISP is Google Fiber (1GB plan).  Fiber jack with the Router is upstairs; satellite is downstairs.  We are a family of 5 and have the normal assortment of smart phones and Roku TV's, and then a couple of Nest Thermostats, work laptops, Treadmill, smart bulbs, etc.  Nothing too extravagant.  

My son is into computer gaming (Call of Duty; Fortnite, etc).  I moved his desktop to a game room.  Tested his internet speed and it's <30 MBps.  There are 3 walls and proably 25 feet or so between the router and his computer.  He has mentioned there is a bit of lag.  He's a good sport about it and is being patient while I try to figure this out, but I'm not too educated on these matters.

As best I can tell, I can either (1) buy a WiFi extender for the room; (2) buy another RBR50 satellite; (3) switch to the Google mesh system that comes with the service and place 3 or 4 of the pucks around the house; or (4) run an ethernet cable behind the walls to the game room so he can connect to a wired ethernet port.  From my limited understanding, the 4th option would be the best, since the RBR50 (supporting WiFi 5) is plenty good for all of my other wireless needs (the gaming seems to be the only issue), so running a connection to that room would be idea.  Can anyone smarter than me on this stuff confirm if you think that is the best option?

One follow-on question.  If it is the best option, then do I assume I don't run an ethernet cable from the Router itself to the game room, but rather run a ethernet cable from the fiber jack inside the house and run it to the room behind the walls to create a fiber jack?

Thank you so much for any assistance and/or insight, and I apologize for the lengthy post...!