Hey Aimz,
I am a pastry chef by trade and at all the 8 different places I have worked at, we have used the cheapest plain flour possible.
However if you are going to make bread, yes you use bakers flour, and for light cakes and sponge cakes you would use high ratio flour. But you cannot seem to get this at the supermarket. But when comparing brands.. plain flour is plain flour. It does the same thing. Self-raising on the other hand, they are all made slightly different and some have more raising agents than others, but that has nothing to do with brands, just batch's. So it's safe to use plain flour and add 1tsp baking powder to every cup of flour that way it is always consistant.

As to freezing flour, yes it can be done if you want it to last over a year, but it must be in an air tight container. If it's kept in an airtight container in the pantry it will also last a while.
This can also be done with nuts, almond and hazelnut meals, when they are put in an airtight container and into the freezer, they can last for years!

HTH