Do you have MCE enabled? It’s usually enabled by default on Asus boards if using the AIO_PUMP 3-pin header, and can cause this type of behavior with cranked up voltages. Just booting up my stock 13900K with MCE enabled resulted in >1.6v until I promptly disabled it.
You can get four DDR5 sticks working without any issues. However, you will have to significantly reduce the frequency to get it stable.
If you need 64 GB, you should consider getting a 2x32 or 2x48 GB kit, as 2x dual-rank sticks are easier than four sticks.
You’re not wrong, but there is a significant price consideration. The 14900K is binned about the same as the 13900KS (6 GHz VID < 1.5v), but costs at least $100 less. Some people claim the IMC is better on the 13900KS, but don’t think that can be answered at the moment.
Socket LGA1700 will work with 12th, 13th, and 14th gen, although 13th and 14th gen may require a BIOS update if it’s an earlier production model.
The upcoming 15th gen will be a new socket, so it won’t work on this motherboard.