Prefered schematic symbol for voltage rail and bus labels
Really, there is no difference between those symbols. All of them mean the same thing. Any engineer reading the schematic will recognise what each one means. I know sometimes different software gives you different symbols, but I don't think it really matters. 

The majority of the time, it is the middle symbol. It is the most common and the one I tend to use. I tend to use the arrows or 'pin' for different nets that aren't a voltage rail, but I am sure other people do it differently. 

So to answer your question, use either of them, but if you want to use the one that is used most often, go for that middle one. 

For your follow-up question, that is the way I do mine as well. For a bus name, just have it written along the top. Just make sure you have it in a place where you can tell definitely which bus the text belongs to (so don't put it right at a point where 2 separate bus lines run close to each other for example).

I hope this helps!