+1 for Linux Mint for the power user. They will fell familiar and can start their journey from there. The most important concept I would explain would be package managers and flat pack, as in vanilla Windows there is no such thing.
The second one would be regular updates and that you have to do a little maintenance from time to time
Mint would be my recommendation for the noob as well. It is a clean distro and does not require a lot of maintenance except regular updates.