A few points to consider:
- S-Mode is somewhat stripped down (sorry, streamlined), designed to compete with Chromebooks and to run better on low-spec. devices (think ARM processors) that could perform poorly with full Windows 10 Home - if your Lenovo falls into that category, you may want to stick with it.
- By default, everything a user does in it is automatically saved to OneDrive to free up local storage
- The default browser supported is Edge, and it's not clear what version of Edge this would be - MS have stopped developing it and have admitted defeat in the browser wars - Edge is now Chromium-based. You can install other browsers, but can't set them to be the default, and that would drive you to drink very quickly.
- Bing is horrid in comparison to other search engines, so not being able to change the default is... unfortunate again.
- You can trial S-mode for as long as you want, it's not an OOTB decision, so suck it and see. If your wife ends up screaming at it, it may be time to switch to full Windows 10 Home before it's thrown against the wall!
- As of August last year, there was a bug affecting some people that meant they couldn't switch out of S-Mode - MS are aware but I'm not sure if that has been properly fixed yet.