had to figure it out the hard way.
Tried to use my oculus quest 2 via wifi, had lag spikes every 10 seconds or so, on both routers... ping went to 300+ for a moment... beatsaber was unplayable like that, every 10 seconds freeze frame and skip ahead.
switched them, et12 is the main router now, got triband smart connect (including 6ghz)and both 5ghz bands of my Ax11000.
Smart connect on every band and no more lag spikes.
guess the ROG Gtax11000 isn't powerful enough to main that mesh