Welcome, Hans, to the OEM forum.
Firstly, the emonLib and emonLibCM libraries were designed specifically for the Atmel ATMega 328P processor. If you have a different processor or a different ADC, you will need to make changes, particularly in the area of reading the sample values, and in calculating and adjusting for the time between reading a pair of voltage and current samples. The reason for the first change is clear - you will not be using the internal ADC, but an external one. The second might not be clear: to read active power accurately, the voltage and current must appear to have been sampled at exactly the same instant. Unfortunately, the voltage and current transformers, which you must use for safety, each introduce a phase lead and this looks like a time shift, there’s also a real time difference if you have only one ADC and a multiplex switch to select the input to measure. All three errors combine and mean you must do mathematical tricks to read the power correctly.
When selecting your ADC, your main concern is sampling speed. You need an absolute minimum of about 700 sample pairs per second to measure a complex mains waveform (i.e. up to the 7th harmonic of 50 Hz). In that respect, your best choice would be the ADS1015.
If you didn’t find it, this might be useful: DIY Current Monitor on Raspberry Pi. My power calculation isn't accurate. Help please? - #11 by Robert.Wall
Of course there is - but the basic principle will be the same, no matter how you implement it. I wrote and explained it in that topic, here’s the particular post: DIY Current Monitor on Raspberry Pi. My power calculation isn't accurate. Help please? - #18 by Robert.Wall