You only need to decide if you want the bike to look cool or work better than it was born.
Choppers are totally impractical but look cool and a well done one will ride well in a straight line but not necessarily corner well.
Brats, well, they are just dumb and don't check any boxes, so I have no clue why its a thing.
Cafe racers are like a more freestyle version of a superbike, and usually have more of a vintage feel to them. Well done ones are some of the coolest builds out there, but there are a lot of hack jobs. Doing a bike right and making lots of custom pieces to really make it your own isn't cheap so get ready.
When you think superbike, think this:
http://kickstart.bikeexif.com/wp-content/uploads/2010/04/kawasaki-kz1000.jpg
Not this:
http://www.motorcycleclassics.com/~/media/Images/MCC/Editorial/Articles/Magazine%20Articles/2007/01-01/Kawasaki%20KZ1000R%20Eddie%20Lawson%20Replica/Kawasaki-KZ1000R-03-parked%20jpg.jpg?h=365&la=en&w=550&hash=35E74A2FB48BBE6A642726BAF79CC2A7EF068ACC
The first represents the highest level of craftsmanship and tech in braking, suspension and power of the era. The latter is a marketing ploy that does many things well, but wouldn't hold a candle to the first one.
Form should follow function, and those that know the difference will see a bike that functions better, and it will look better in their eyes. Lots of bling and shitty bolt-ons like pods, balloon tires and the like are not the route to take if you want your work to be appreciated. Notice I said appreciated, that is not about you getting cool points, its about knowing that you built something to a high level. If you build a clown bike, that reflects on you that you aren't a person who listens more than speaks, who doesn't do research on everything, and is willing to settle for less than you are probably capable of.