Hi Eileen,
I am Dave, I will help you with this.
The only difference between Windows Home and Windows in S Mode is that in S Mode you can only install Apps from the Store and not 3rd party software, and because you cannot install or execute 3rdparty software, that makes Windows a bit more secure.
However, most people find Windows in S mode too restrictive and they need to switch to Windows Home edition.
Windows Security has many components, of which Defender is only one part and it is Windows Security that is currently protecting your system, have you experienced any difficulty up to now?
Windows Security is not low down on the list, on most Security forums, when compared to 3rd party anti-virus suites, it is rated up there with the best of them
The main thing when switching out of S Mode is to only install software from the software developers official website, and you will not experience any difficulty or any extra threat on your PC.