I have a Wattbike Pro and train on Zwift every day through winter so I'll try to answer you questions.
First of all Zwift is fantastic I can't recommend it enough its almost as good as riding outdoors and in winter its a million times better than riding outdoors. The whole Zwift experience is totally immersive, you can just go for a ride, ride with your mates, race, do group workouts or follow one of their many training programs etc etc there really are no limits. To get the best out of Zwift you'll need a decent trainer with a power meter, and cadence sensor and ideally a heart rate monitor for training. The trainer will need to be able to transmit via Ant+ or Bluetooth to connect to Zwift. To run Zwift you'll need a PC, in which case you need an Ant+ dongle (you can get them from wiggle)
http://www.wiggle.co.uk/lifeline-ant-usb-stick/
or you can run it using an iPad, iPhone or through Apple TV. I use a PC with the dongle and also use an iPod to run the Zwift App which allows you to control certain Zwift game features easily and communicate with other riders in real-time.
There are loads of different trainers out there and most are now smart trainers which means the resistance automatically changes depending on the terrain on Zwift. Basically if you go up a hill on Zwift the resistance increases and the steeper the hill the more it increases just like the real world. Most smart trainers are compatible with Zwift but you can find details of what you need here:
https://support.zwift.com/hc/en-us/articles/203152565-Which-trainers-does-Z...
and here
http://zwift.com/hardware#ready
If this sounds complicated it genuinely isn't and there is loads of help on how to get started on Zwift. When you sign up I think you get a certain number of free days but then you have to subscribe its about $20 a month which is a total bargain.
I have the Wattbike Pro and this isn't a smart trainer but the recently launched Wattbike Atom is a smart trainer and is actually cheaper than the Pro. The advantage of the Wattbike is (1) its super accurate so if you genuinely care about your training and performance and want meaningful power data it really is the gold standard (2) it is a self contained trainer so you don't need to use your own bike which means you're not wearing the parts of your bike, chain, cassette, chain-rings etc (3) its super adjustable so you can dial in your bike fit perfectly and experiment with different geometry fits very easily (3) it has a load of technical features especially the way it measures pedaling dynamics which are very useful if you want to improve your pedaling technique. I transmit the Wattbike data via Bluetooth to an iPad running the Wattbike App. If you go for the new Atom model you will need an iPad anyway as it does not come with its own monitor.
I did the 190 mile Dragon Devil ride in 2016 in just under 10 hours, its a brute but great fun. Best advice is to go late so there are plenty of people on the road in front of you to use as carrots to bridge up to. Make sure you start easy and try and get into a group of riders who are of similar ability then work together.
Irrespective of which trainer you go for get on Zwift - its ace!
Good Luck
Lee