Ping the IP of your router to see if you are getting problems on the wifi or if it is another problem. If you see wifi issues with a ping command try moving the pc next to the router to see if it a location issue.
Wifi issues there are very few things you can do. It is the standard update the driver, try using 2.4 or 5 radio. Try changing the wifi channels on the router and see if setting the channel width to 20mhz helps.
Online games are more affected by wifi issues than any other traffic which is why it is recommended to never plan games on wifi. The only true solution is to not use wifi try powerline networks or maybe moca. A actual ethernet connection is always best.
If the ping is good to the router then it get complex because it could be a issue with almost anything on the machines and it is only blaming the network when it is some other issue.