Hi Scott
I am Dave, I will help you with this.
Windows 10 in S Mode only allows you to install software (apps and games) from the Microsoft Store, you cannot install 3rd party software like downloading software from other websites, or using conventional software installers.
Because you are limited to installing software from the Microsoft Store, then your PC would be a bit more secure, but if you are a sensible user and only install software from official websites, then this is not a problem.
Most people need to switch Windows 10 and 11 out of S Mode to be able to install the software they need to use, switching out of S Mode is free and you would end up with Windows 10 Home, however, switching out of S Mode is a one way operation, there is no way back to S Mode.
if you want to switch out of S Mode:
Open the Settings App
Go to Update and Security - Activation (Windows 10)
Go to System - Activation (Windows 11)
In the Switch to Windows 10/11 Home or Switch to Windows 10 Pro section, select Go to the Store. (If you also see an "Upgrade your edition of Windows" section, be careful not to click the "Go to the Store" link that appears there.)
On the Switch out of S mode (or similar) page that appears in the Microsoft Store, select the Get button.
After you see a confirmation message on the page, you'll be able to install apps from outside of the Microsoft Store.