Carl at Geotech has not definitively stated what frequencies are being used. He has speculated that there are certainly at least 2 in each mode.
Minelab will absolutely not be releasing the exact frequencies. That would be a really dumb thing to do. It would give away too much of their patented proprietary engineering and software data for Multi IQ.
I use my Equinox for many types of detecting but especially for SW USA gold prospecting. Most of the nuggets I find are smaller than .5 gram. Using the Multi setting, Park 1, Field 1, Beach 1 and Beach 2 will detect .5 gram gold and lead pieces fairly easily even in mineralized dirt down to about 3”.
Park 2, Field 2 and both of the Gold modes will detect .2 gram lead and gold at 3” and .5 gram gold and lead down to 6”. That tells me (much like the manual) that Park 2, Field 2 and the Gold modes are using plenty of the highest frequency (40 kHz). The other modes are probably using 20 kHz or less for their highest frequency of the two simultaneous frequencies since they are not as sensitive to those small gold and lead targets.