they're so many different top water lures out there (walk the dog, poppers, and buzzbaits) How do you know whats the right one for the right situation?

If the water I am fishing is calm then I will use a more subtle topwater such as a spook or a popper.  A jitterbug reeled slowly is also a time tested bass catcher here as well.

If the water has some chop, I will use something a little more noticeable like a devils horse or a buzzbait. You can also work the spooks and poppers in a more aggressive manner in chop as well.

Spooks- Glass surface, slow retrieve:Choppy, move the bait a bit more aggressive. A rattle helps in the chop also.

Poppers- Gentle twitches a bloops when its calm, aggressive almost walk the dog type retrieve when there's more wave action.

Propbaits- Again, gentle when the surface is calm, but get that thing movin' with a steady twitch, twitch, twitch,.....BLAM.

Buzzbaits-Better for days when there's more chop on the water, as the aggressiveness of this presentation can dissuade bass, especially of the clearer or more pressured waters. 

I use poppers when the water is calm to little chop, and turn to buzzbaits when its getting darker or I need to cover more water. Prop baits are better than poppers in choppy conditions, and spooks are what I turn to when action from the bait rather than noise is the key.

Another factor is the amount of water you're fishing. For example, if you're fishing a small area you can use a popper and give it numerous small pops and still keep it in the area. Then there's covering water where buzzbaits, Jitterbugs and walking baits are good.

But regardless, you have choices for a given set of conditions and there's no one correct bait. You may have to make an arbitrary decision and then make changes depending on what happens.