For Intel's upcoming processors and motherboards based on DDR5 memory you'll probably want seom compatible products. Good news, Intel has posted a QVL (qualified vendor list).... Intel releases XMP 3.0 DDR5 QVL compatibility list for Alder Lake CPUs
Overkill? No, they couldn't even run the 111900K at 5.1 stable GHz. I'm kinda sure that they won't improve this on the Z690 neither, since they just release the same chipset with different pins and call it a day and evolution.
I have z490 Apex and z590 Apex, and both have no problem running 5.3ghz on my 11900k chip stable So I don't know what you are talking about. Both doing 5.5ghz on my best 10900k too. 5,6ghz Cinebench R20 on watercooling. Maybe you are thinking about something else? Did you test for yourself, or did you read on reddit? Apex z690: has VRM 24x 105A, = 2520A