Hi, read your post and have a few thoughts for you. As a computer repair person (laptop specialist) and sometime salesman may I recommend the following:
A tablet would probably not be capable of what you want - unless you want to pay more than you do.
Chromebook - Several problems here. Usually a small hard drive as they are meant to be used with the 'cloud' to store pics, documents etc. Needs a good internet connection and if the net goes down then no access to your stuff. They are cheap, but imho not worth it.
Laptop/tablet hybrids - These are nice machines, but frankly they tend to be on the pricey side with a decent size screen and a DVD drive.
Windows laptop - Frankly these are the best option for the average user. Windows can be a pain in the bum, but it does work and there is a program you can get that gives you a proper start button so it behaves like the Windows most people are used to. It's called Start 8. For a (very) small cost it's well worth it - I use it myself, and It's something I always recommend to people.
Now, with regards to 'future proofing'. There is, again imho, no such thing. All you can do is to get the best machine you can afford/want to spend. I would recommend a MINIMUM spec as follows:
Core i3 processor
4 Gb ram
500 Gb hard drive
DVD drive
15 inch screen
At LEAST 3 separate USB ports, 1 of which should be USB 3.0 (higher transfer speed)
As for the operating system, unless you can get a machine with Windows 7 pre-installed, make sure you get Windows 8.1 - it is better than 8, even if only a bit.
Anything else is down to personal preference. Try to get a machine with a graphics card that has its own ram if possible - it means the machine will run quicker and better.
Check out any local computer shops as well as the national chains - you might pay a bit more but you are more likely to get better service if anything goes wrong. PC World are great for buying cheaply, but crap for after sales service, and they will try to get you to buy the extended warranty. In my experience, laptops fail on first boot (I.e. dead on arrival) or after 4 years or so, unless there is an accident that damages it.
Always, always, look at a machine you like personally and give it a try. If they won't let you try, walk away. If you've any questions, DM me and I'll try and help.