Another vote for GMail and the Google Apps suite - Everything I have is now on Google Drive, I use Google Apps (Docs, Sheets, Slides etc) exclusively - have not touched Word etc for well over two years now, Calendar, Keep (notes) etc all work effortlessly across all my devices. Whether I'm on my Mac, my phone, my tablet, my chromebook, or on a borrowed PC at the office, it's all there, 100% of the time.
There is no 'syncing' as it were to worry about it (well there is a little bit that takes care of itself for off line working) as usually you're working live on a single cloud hosted copy of your documents. 'Hand-off' is great - and by that I mean you can work on the same documents on as may devices as you like simultaneously - start on a Mac, edit on a phone, update on your home PC or tablet while sitting in front on telly, review on phone on the way to work etc. It matters not, and you'll never have any issues around versions etc. Collaboration with others obviously works the same way.
I'm a bit of a convert (as you might guess); I presume you can do the same with Office 365 etc, but don't know the details behind that, but it is certainly a little less device agnostic when compared to the Google offering at the moment (the trade off being you do get access to the 'full fat' versions of the office tools on the PC).
For me - the total device agnostic approach is the way. My wife just swapped from a Mac to a PC, and there was literally nothing to think about, not even the data migration aspects, it's all there on Google drive ready to go. Same when she swapped from a IOS phone to an android one. For your general office stuff (email, calendar, notes, docs, sheets, presentations, etc)- use Google (or Office 365), and pick the device that works best for you for the tools that are more device heavy (gaming? perhaps PC, CAD - workstation, well - anything really). There are native apps for the Google suite for most phones - these are excellent and allow off-line working, there's the stupidly cheap chromebook if you want an laptop experience, and for everywhere else, there's the Chrome browser.