AIOs LCS are closed loop and don’t need any special maintenance. In any case If you go for air cooling then whatever the number of fans you place in the case follow the rule of +1 fan intake over the exhaust fans. I do the opposite +1 fan exhaust, at the expense of dealing with a little dust. For the case use always 140 mm fans at medium/low rpm vs 120mm at medium/high rpm. Better performance and more silent.

They are the stock limits for 13700K and 13900K but the motherboard may come with other values as default.

Check Power Limits in BIOS. PL1 should be set to 125W and PL2 to 253W.

So you are telling that your PC is snappier due to RAM? Because his DDR5 is objectively much faster than your DDR4. Try the same 7-zip benchmark on both systems and you will see at what extent the difference is there