(I recommend MATE for the desktop interface, it's basically the software that Ubuntu [a Debian "derivative", hem hem] used when people thought it was great.)
Used to be the goto distro for those who just wanted a "plug-n-go" experience was Ubuntu. Unfortunately, Ubuntu has lost their minds when it comes to the desktop interface. But - you may like it. Try it out (live thumbdrive or such). It's possible to go back to the "old" interface if you want, and it doesn't take much effort - but may be more than you really want to play with.
The other distro I have heard great reviews on that still has a sane interface is Linux Mint - again, try it before you "buy" it.
Virtually every distro except for a few niche ones have Live boot versions, that will allow you to try them out on your system, get a feel for what works, what doesn't (hardware and software-wise), and how the overall system "feels" - before committing to an install.
Your other option (to handle your use cases) might be to keep a windows partition (or on a separate drive) around and use that. Another option would be to use Microsoft's online Office360 suite (I think that's what it is called?). Or run VirtualBox on the Linux system, and run a version of Windows inside that. Any or all of these could be done together, in addition to using Crossover and/or Wine. You have a ton of choices here.
Also - for your documents - you say you are worried about formatting when they go to the client - does the client need to be able to edit them? If not, then dumping them out as a PDF might be able to work for you, if they'll accept PDF copies vs Word docs. The other thing to do would be to take a few of your old copies of docs you have sent to clients, and run them thru LibreOffice or something - see what they look like when you import them, then export them back out to a new file in the various Office formats, and load them back up in Word and see what it looks like. You might be surprised at what you find (you might be disappointed as well). This is all something you can try with the Live boot versions of Linux distros.
Oh - and games - besides using Crossover/Wine - there are a ton of native games available, plus plenty of "old-school" conversions and ports (some quite fun and amazing - some of the Doom/Doom 2 ports are pretty amazing). Also, there are a ton of Steam games on Linux available, too. If all you do is casual gaming, and don't care about always running the latest AAA shooter/fps/mmorpg or such - you'll usually be able to find something worthwhile and fun to play.
