It would be best if you remain with Sierra for a while longer. A number of individuals here are running into issues with High Sierra, and it really does not offer anything "dramatic" over Sierra. Sierra is very stable, and is rock solid. I actually did upgrade both of my Macs to High Sierra (did a fresh, clean, "virgin" installation), and while I am not having any issues (and certainly none which others have encountered), I am somewhat disappointed with the "speed" of the OS (although it is improving).
Yes, you can place an empty folder onto the desktop. In fact, it is even easier than "placing" one: with your mouse placed anywhere on the desktop (where it is empty), right click on the mouse, and gold down that button. A small dialogue will appear, looking like a menu. The first choice is "New Folder". Select that, and voila, a new folder appears. You can then move the mouse to where it says "Untitled" under the folder symbol, and give it another name, if you want.
You mentioned WORD documents. Are you using Office 2016 for the Mac? I have it on both of my machines, and it works fine. I use Outlook 2016 a lot, and Word and Excel occasionally.
Additionally, I assume you plan on making backups. The Mac OS comes with Time Machine, which can be used for backups (there has been something similar in Windows that I suspect you know about). But I prefer to use SuperDuper!, which makes a bootable backup/clone of my entire "system", including the OS. It certainly makes recovery easier.
Finally, it is important that you perform disk maintenance/cleanup/repairs, from a software perspective, on a frequent basis. You can do a good amount of disk cleanup on your own, and there are some excellent programs available (both free and commercial) that can help you with those tasks. Here are 4 excellent free ones that you might want to consider using:
Onyx: Available from here:
https://www.titanium-software.fr/en/onyx.html (make sure you get the correct version, which for you would be V 3.3.1)
AppCleaner: Available from here:
https://freemacsoft.net/appcleaner/ (comes in handy when removing an application, and all its associated "stuff)
GrandPerspective: Available from here:
http://grandperspectiv.sourceforge.net/ (Neat, graphical way of seeing what files are occupying space)
Malwarebytes AntiMalware: Available from here:
https://www.malwarebytes.com/mac/ (Excellent for finding any "adware" that can crop up on your machine via using the internet)
Forgot to mention one other important item: when you delete an EMail, it is not permanently removed from your system (assuming you do not leave your EMails on Comcast's server/servers). If you do that over the course of a number of years, those can take up a good amount of disk space, which you don't want. In Outlook 2016, it is actually quite easy to have deleted EMails permanently removed (I use it for just about every time I launch Outlook 2016). I don't know how to do it with Thunderbird, so you might need to research that.