I have 96GB 6800 CL34. XMP no problemo runs on first boot (14900K, Asrock Z790 LiveMixer). Even tried to push it a bit to 7200 with lower timings but I have to spend more time on it.

Maybe. But a 240mm AIO has no advantages over a good air-cooler, and all the downsides of an AIO. Eg. pointless.

My 14900k does 40k in cinebench r23 on 240W powerlimit :P Aint no 13900k coming remotely close to that.

Idle usage of all of them (even the 14900k) is really really low, like below 5 Watt. And of any of the CPU’s (even 14900K), you can just set the TDP (PL1 & PL2) to whatever you want. Obviously it’s slower at lower TDP. A non-K cpu is just equal to a K cpu but it has different (lower) default settings for the TDP. You are fully in control of how hot and fast the CPU is (under load).

For gaming, an AMD CPU usually generates higher FPS for the same TDP. Something like a 7800x3d is pretty efficient.

No, undervolting improves performance. It will *always* consume to what you set the TDP. So, by lowering the TDP and then undervolting, you can keep the same performance at lower TDP (and that’s a lot more than 5W for a 100mV under-volt).