No, it doesn't affect tone plus if you don't know some peoples remove two tubes from their 100 Watt amps for the reason they can't handle the power they have. So, what is the result? Again, 50 Watt amp.
Sites, I dont know many. I buy from Thomman.de an online store based in Germany. So, I am afraid I can't help you with this.
Depends on the space you have available for play with it. They are not different, they are the same. The one is 50 Watt the other is 100 Watt.
If you dont have big room, I recomend for you the 50 Watt.
Have a nice day.
you will need an attenuator my friend if you are going to play in your room at low volumes. but i heard it sounds amazing at low volumes so you might not need it at all. you will see when you play with it.
a 4x12 means a cabinet; a box with 4 speakers 12'' inches inside it. 1x12 is one speaker only.
have a nice day.