Having large lag spikes on WiFi every 10-15 seconds

When the PC is wired directly to the Orbi router, gaming operates as you expect, but when using WiFi, there are regular interruptions about every 15 seconds.  And, both the PC and a Mac have the same problem on WiFi.  How did you arrive at the measurements of 22ms vs. 2500ms?

The obvious conclusion is that something is affecting your WiFi signal every 15 seconds.  Many WiFi analyzer apps are set to sweep once per second.  When you watch the "moving graph" of the signal levels of access points (yours and others nearby), does your router signal drop every 15 seconds.  (The analyzer on my Android phone app calls it "Time Graph".)  It is normal for WiFi signals to "appear and disappear", but a regular pattern may indicate that some neighbor's system is affecting yours.

With a house full of devices, there is a chance that you have inadverdantly created a network loop that is allowing broadcast packets to create a "storm" that overwhelms the WiFi signal.  Some networked sound systems have been reported to have issues when connected to the home WiFi network and their own private WiFi network at the same time.

When you connect to the Orbi "debug page" (usually 192.168.1.1/debug.htm), what does it show for CPU load?  (i.e. every time the screen pops up, immediately refresh the screen.  For example, my Orbi reports values from 6% to 45%, but is typically between 10% and 20%.