What's the correct order of NAM Installation, NAM and then Essentials, or the opposite?
Furthermore, is installation of the Essentials necessary?
Also is there a "recommented" method for switching LH to RH driving? For the European version of SC4, selection of "English" language makes the installation left-hand-driving. So players who want to change this must find a workaround. The mod I have used till now is "Road Switch (Left to Right)" from ST Modds and Downloads. It's ancient, but it appears to work.
How does this combine with NAM Installation (eg install first the LR Switch, and then NAM)?
For the current NAM installation, you don't need to install the NAM Essentials at all. They are mainly intended as a separate download if there's a NAM Update or another file that contains new features for additional plugins, such as new custom bridges, the RHW, SAM etc.
This is the recommended way to change driving side. (http://sc4devotion.com/forums/index.php?topic=3961.msg124449;topicseen#msg124449)