Thou shall not assume liquid cooling is always better than air cooling. Often times, great air coolers can outperform less-performing AIO coolers.
Thou shall not assume that 'having liquid cooling' means that it automatically is 'good liquid cooling'.
Thou shall not assume that an AIO liquid cooler will perform as well as custom watercooling, nor that a 120mm AIO, 240mm AIO, 280mm AIO or 360mm AIO all perform the same.
Thou shall realize that as in all water/liquid cooling, flow rate, fan speed/CFM and radiator size all play a part in cooling performance.
Thou shall realize that most AIO coolers are made by the same, few manufacturers and then rebranded, which mainly differ in software and fans used. Pumps and radiators are often exactly alike.
Thou shall realize that custom watercooling is often expensive and cutting corners with cheap no-name components might result in unknown (and unwarranted) disasters.
Thou shall reallize that you can find mounting hardware (bolts, nuts, washers) at your local hardware store if you need to customize to your needs.
Thou shall realize that you should know your cooling loop's complete TDP needs. This is not the same TDP needs your entire PC will require from a power supply...only the heat outputs being addressed from cooling blocks.
Thou shall realize that cooling loop delta-T is a result of ambient room temperature, cooling loop total radiator cooling volume, coolant flow rate, fan airflow/CFM and TDP of components being cooled. This defines the difference of coolant temperature vs. ambient room temperature. Good performing delta-T is 10C difference between room and coolant.
Thou shall realize that your reported CPU temps vs. ambient room temperature is a delta, but different than the delta-T of the coolant temperature of the cooling loop vs. ambient room temperature.