They are one and the same. In your dhcp server you are “reserving” a specific (ie static) ip address that it will only give to a network interface with a specific MAC address. This is opposed to a dynamic ip address wherein there is a pool of available ip addresses that get handed out on demand and as such what is given to any device will likely change from time to time. Although this is not strictly necessary as you can use host names instead of ip addresses, it is less error prone in a home environment as you don’t ever have to rely on any mechanisms for host name lookups.
Although the end result is mostly the same, with current versions of Windows 10 they make it a real pain in the taint to quickly add a local account. Banging out that single line in an elevated command prompt is a fraction of the effort.
Then why did you ask for “If I am starting from scratch…”? Your getting free support from people who are volunteering their free time to provide it. Focused questions save everyone time and effort.
A Kodi “source” is just a specific file path that is designated to be used as a media location. These would be analogous to Windows library folders where you have separate “special” folders dedicated to music, videos, pictures, etc. There isn’t actually anything complicated about them. You tell it to add one and point it somewhere. The procedure I outlined just makes it easiest to setup as it both allows for browsing SMB shares lacking NetBIOS and it adds credentials to Kodi for the entire machine instead of having to do it for every source.
If you create a source in Kodi to smb://somewhere then Kodi itself is handling the networking part of the communication. For most this is simple, effective, and all that is needed. This method is not the most performant though so one can optionally attach their network location in the OS and then point Kodi to the location its attached in the local file system. In this way the OS takes care of the networking part of the communication. In Linux this is called a mount and it is (very) roughly equivalent to mapping a file share in Windows.
This has advantages when you are lacking bandwidth such a a Vero 4K user trying to play high bit rate 4K rips through the fast ethernet connection. For anyone who isn’t getting buffering issues this usually is providing little practical benefit. The downsides would be more effort if you have to restore from a backup and if you are running various clients across platforms it makes it more of a hassle as you can’t just simply copy your config from one machine to the next untouched. I would also highly suggest Kodi SMB paths to anyone moving to a MySQL setup as they are the only source type that works across all platforms. And, as mentioned, you can use path substitution to switch at any point on any client.
The static ip and saving your credentials prevents this issue. In your Windows user settings there is access to your saved credentials. Take a look, it is pretty straightforward.
Supposedly Microsoft 
Linux now but until they add NFS support to Win Pro and contribute official SMB and NFS to Linux their declaration is a bit lacking. The built-in SSH client in Windows works fine and it is all I use. I did tweak cmd a bit to allow for a longer history and more readable colors.