Macbook Air Full Factory Reset?

I want to reset my Macbook Air Early 2015 but not just simply deleting the disk and reinstall it with macOS Utilities menu. What I mean is "full factory reset." I want it to be like it just left the factory, at least in the software side. Like SMC and NVRAM reset etc. Or deleting the disk resets the things that I mentioned? If not, when should I reset them? After deleting the disk and before installing the High Sierra (I will downgrade from Mojave to High Sierra) or after installing the High Sierra? And are there any other things that can be reset like SMC and NVRAM? If there are, please mention them.