Yep, avoid the iPad. Not only is iTunes completely frustrating to work with, the iPad just doesn't have the features of Samsung's tablets or the price competitiveness of Windows tablets. Another big advantage of the latter two is that they can carry a microSD card for expanded storage, which I have found invaluable.
Yeah not needing the keyboard and paying for it is an issue. I don't think there's a 3G/4G model of it either, but at least you'd have the USB modem that would for sure work with it. But do consider that it is priced competitively for a 10 inch tablet, at least in the US, the pricing goes for a 7 inch Tab 3 is $170, an 8 inch Tab 3 is $270, iPad mini (7 inch) it's $330, T100 is $350, the 8 inch Note is $360, the 10 inch Tab 3 is $360-450, the 10 inch note is $500, while the 10 inch iPad is $600 (prices for WiFi only models.) Personally I wouldn't pay any more than $400 for a tablet.
I don't know how it works in Europe, but in the US, even if you already have a data plan, to add a tablet it's another $15-20 a month, and that doesn't add any extra data to your plan. As far as SIM cards go, I'd assume them to be similar, but the only way would be to check one out yourself, try popping your SIM card into one at a store, or asking to see a friend's.
That's where you might have issues, the software. I doubt there's compatibility with Android.
The pen is really darn cool, and can be bought separately, but only works with Note phones and tablets. It allows you to write in handwriting and it can either save it like that for notes, or translate it to text as you go. You could also use it for drawing. It's something you'd have to try out to see if you like it.
So try out the pen on the note, and get a look at the SIM slot and see if it's compatible. If it is, don't let them make you buy a new data plan when you buy a 3G/4G model, and just go with the card you have now and swap them when you want to use the other.
Good luck, and have fun shopping!