There are two models of the Note. One is a US version sold by at&t, and the other is an international model sold in the rest of the world. I believe the canadian model is the same as the at&t model also, just without the at&t logo on the device. Any easy way to tell is the large button on the front of the device instead of the four capacitive buttons.
Android in itself is not an entirely open system out of the box. You are still limited to the Google Play store or Amazon App store for mainstream apps. If you want to download apps from other sources, you have to root the device, which is essentially unlocking the device to allow more customizations than stock.
TouchWiz is Samsung's Android interface. All companies install a interface of sorts to allow for customizing the OS to the end user's liking. The only devices that have the pure Google experience are the Nexus devices. The Nexus devices are essentially setup the way Google wants them to be, with little or no customizations.
I have used Samsung Android devices for a few years now and I don't mind TouchWiz at all. Some people just abhore it. Why, your guess is as good as mine. They will hate TouchWiz, but love Sense (HTC interface), or hate them both and love the non interface Nexus devices.
The final decision is up to you. Use what you like, not what other people tell you is bad or good. Your best bet is to go to a retail carrier store or a BestBuy/Radio Shack/major electronics store in your area that sells phones and play with the active display models to get a minor feel for the devices.
The real problem is going to be when you get the device home and use it day to day. That is when you will really get a solid feel for the device. You can always return it, but restocking fees can be a bummer. So the more you can play with a device before purchase the better.
There is always the ability to flash new ROMs on Androids also, but that is a longer story for another day.