Probably most devices will not be able to keep their full wireguard speeds while donloading/uploading to WAN at high (Gigabit) speeds as properly stated on the first post about the real world VPN use.
Sure. This script only gives a way to test wireguard performance locally as I noticed it in the readme of my repo. Not everyone has another machine and high-speed LAN to have a benchmark in real scenarios. I just found this way simple and the difference from the real scenarios benchmark is very small for MT7621, MT7981.