Try going into bios f2 on startup and disabling your core overclocking level (presumably it is set to OC1 or OC2).  Also, disable it in AWCC too.  

For some reason, I can't change it. It is all grey and I cant click any options 

Ok, wow 5.1 ghz.

If you haven't otherwise changed any settings in bios from stock settings, are you able to reset it to optimized defaults there should be a selection in the prior screen for that.

For some reason your bios is stuck on a custom oc setting which appears to be too much for the cpu to handle or otherwise allowable so it's returning the error.  Were you toggling selections in AWCC before this happened? I've seen this happen as a disconnect between awcc and bios selections when selections are toggled back and forth in awcc in windows (even if nothing is ultimately changed and everything is put back), the first time after the pc restarts it loads or tries to load a custom setting. For some reason awcc retains the selections and tries to apply multiple ones at the same time resulting in a custom setting when the pc eventually gets restarted (could be days later).

After reading your comment, I was able to rest it to optimized defaults and disabled core overclock level. What do I do now? I won't touch anything from the OC profiles in AWCC.

Did it fix the oc cannot be applied error and the only issue is the fan error now?

Yes, I think the OC cannot applied now error is gone. No notification from AWCC startup. However, the fans error still pop up every time I start the computer. 

Dell's Bios doesn't let you switch off the fan error or check, you'd have to find some workaround to bypass it or get it to pass the check (which is programmed to check for a range of correct responses to pwm that the oem fans give). One thing you could do is stick the noctua in the 3 pin end of the y splitter and stick the other ml120 pro cable into the front fan header, then put top and front on the same curve.  Or return the noctua for another ml120 pro.  

The R11 is so new not many people have done the fan replacement yet.

I did the top fan only with the recommended ml120 pro and worked great.

Sounds like your ml120 pros for top fans is also working fine.

But the issue seems to be the Noctua NF-A12x25 PWM giving an error?  In previous Aurora models, this fan has been fine.  Maybe something has changed with the Bios in the R11?

It would be good to know and I'm also considering replacing my front fan with the Noctua NF-A12x25 PWM.  If it determined that fan is no longer playing nice with R11, then I'll have to get another ml120 pro.

I have a newer r11 with the 3080 and I replaced the front fan with the Noctua NF-A12x25 PWM.  It is throwing up the warning error.  Any suggestions?

Or do you buy 2 corsair fans for the CPU and one for the top fan? IM confused because the first post discussed the person buying 2 corsair and 1 Noctua? I didn't think the aurora R11 from what I've looked at on mine can fit 2 top case fans only the one ?? which case fans should I buy for the topfans above the cpu fan?

How do you put in 2 corsair fans n the Aurora r11? It looks like only one top case fan will fit? I have the regular fan heatsink customization. 

Considering I did not get AIO, since it is still in its development, im not sure what my options are right now. I still want to be able to provide the best air cooling I can get right now, and idk what that would be. so im wondering what I can do with what I did get

and, idk if getting an AIO system and replacing it would be a good idea lol, because idk if the system is compatible with it and what would have to be removed or moved around either and idk if that is realistic or if I am able to do that either. sorry for all the questions im still learning about all this and im new to PC's and trying to figure it all out.