Think Be_Glorious below is correct, this seems like a packet loss issue.
Do you have a lot of other wireless devices connected? Are there a lot of other routers or bluetooth devices around you (like if you live in an apt, for example)? You can use tools like Stumbler dot net to check for interference on the radio bands you're using, and then go into the modem setting to change the wireless "channel." This is usually way less of a problem on 5G, but you seem to have an exceptional case.
Also, you said your router was 2m away from the headset, right? Are there any walls in the way? 5GHz radios are much worse at wall penetration than traditional 2.4GHz bands - you might get better results switching the headset to non-5GHz mode, or seeing if you can move the router or headset to be unobstructed.
If those don't work, I'm pretty out of ideas. It seems like you've done a hardcore job of controlling for various hardware and software issues. Maybe see if someone else's Oculus has the same problem?
The best and most reliable solution is to run a wire. Wireless is not really suitable for situations like this.
You can probably rig something to work using a wireless extender, but first I would try scanning the wireless environment to make sure you are on an unused channel. Wireless is susceptible to interference from neighbouring APs, so if you do see APs out there that aren't yours you can configure your AP to run on an unused channel.
Wireless is also susceptible to interference from non-wifi sources (microwaves operate on the same frequency as 802.11b/g), so if you have a shitty old microwave and you find that its usage corresponds to your wireless problems then go buy a new microwave.
But seriously, run a wire and save yourself the heartache of trying to get wireless to work.