Found MX with the Flux box window manager works better 'out of the box' for the 17 inch iMac than the xfwm4 such as seems zippier, easier to resize windows and smaller download (no LibreOffice but can be added if you need it.) But also found a Conky that has a working temperature reading.. ok - so not the GPU as Id like..but may have some pointers to get that .
I used Mepis on all my systems back in the day. Way before I experienced modern OS X / macOS. One the most stable OSes I have ever used! Good OS and great people!