NEED ADVICE ABOUT CHANGING AUDIO

Can someone explain to me the difference between the old sound font setting of 2, 4, and 8 that were on the original Cakewalk Express and SB Live, and the way that Sonar Home Studio 4 XL accesses different sound banks for midi playback?

Does one sound bank become exclusive throughout the entire project or can several sound banks be used independently from each track in a project?

How are the sounds accessed? Do the sounds come with sound cards, only?

Can the software be purchased to reach a studio quality sound selction for each track?