The open energy monitor site you've mentioned is possibly the best place to start for background reading/research. Ideas and snippets cam be used to roll ones own setup if inclined.
This link provides some good info to somewhat similar question-
I built an Arduino/picaxe based solution before finding the OEM project, but would now certainly use a combination of pi/Arduino if I wanted to replicate or upgrade my project.
A WeMos (Arduino compatible) wi-fi module/board (https://www.wemos.cc/) would be a good way of interfacing a single current clamp or domestic power meter "power flash" sensor wirelessly to a pi.
I've used several of them around the home from time-time experimentally to measure temp humidity light etc and can really recommend them as a more capable alternative to an Arduino, especially if direct network connectivity desired rather than rf links. Cheaper than pi too.
Ultimately, depends whether you prefer something plug and play, or a project.
Otherwise, if you want to use a pi directly and your home power meter does have the flashing power indicator, sensing that via gpio would most likely be the quickest, cheapest and easiest way to get started, even though the update rate gets slower as usage goes down.