My issue is that I’m not sure if SketchUp 2015 has simply updated the templates in preferences and they are all the same as before with different names OR if there are missing templates from my preferences window.
The templates not in my preferences are: Plan View, Engineering, Google Earth and maybe others.
Yes there are changes in the set of distributed templates from time to time.
You can copy over the old templates to 2015 templates folder, OR open one of the old templates in 2015 (by specifically browsing to the 2014 templates folder,) and then Saving as a template in 2015.
Go to the SU program folder and drill down into …\Resources\en-US\Templates to find them. Open those MIA files in SU15 and do File > Save as Template, which will update them to SU15 standards.