Stop downloads from causing lag
When someone downloads or uploads, your router lets a queue build up and every game packet and call waits behind it (bufferbloat). Smart Queue keeps that queue short by limiting the line to just under its real speed.
Your Smart Queue numbers
Enter the speeds your Lag Check measured, wired if you can.
Pick cake (or fq_codel) where the router offers a choice. Some routers ask for kbit/s, others for Mbps.
Enter both speeds to see your limits.
OpenWrt router? Let the helper do it
With Smart Queue installed on the router (luci-app-sqm), run this on a Raspberry Pi or Linux computer on your home network with Docker. It measures your line, tries 90%, 85% and 80%, keeps the first setting that fixes lag under load, and puts everything back if nothing helps. Your router password stays on that computer.
docker run --rm -it --network host -e ROUTER_PASS='your router password' ghcr.io/ismailgalaxys25-del/netpulse-agent:latest -tune-sqm
Add -dry-run at the end to see the plan without changing anything. If the router isn't found, add -e ROUTER_URL=http://192.168.1.1 with your router's address.
Guides for your router
Where the setting is, what to enter and what to watch out for, brand by brand.
Don't know your speeds? Run the Lag Check first. Router by router steps are in the bufferbloat guide.