5700X = less power draw than a 12700K for mITX use. Like....almost 100W less.
5700X is ~$100 cheaper than a 12700K.
Note that you [should] be using PBO on AMD CPUs.
AMD mobos are generally cheaper than Intel 600 series.
Offering alternatives.
Didn't like the price/performance of the 3080Ti options. The 3080 12GB is too power-hungry IMO.
Offering alternatives.
Note above that this budget puts you in the class of hardware that's best used with a 1440p monitor with 144-240Hz refresh rate, or even 4k. Hopefully your friend's monitor is somewhere in that region. I purposely landed on the low end of the budget range in case a monitor upgrade is needed.