Thanks, I give it a try with a Linksys EA8300 - underestimated how difficult it is to quickly acquire a suitable device... And I wish it would be really a ~20-40Gbit as written above (~20-40Mbit of course...).
For documentation purposes (if someone is looking into this as well):
Current setup is running with 100M down/50M up (uplink: 400M down/50M up) with the EA8300:
Laptop -5Ghz-AP-> OpenWRT -> wireguard -> 2.4Ghz-Client/Cable modem -> Internet node/wireguard server