Keep in mind that some routes have both... it all comes down to what aircraft is used (take, for example, SCL-LIM. It has PB on widebodies and PE on narrowbodies)

Rule of thumb (with some exceptions)
1.- any domestic route will be 100% coach (exceptions include SCL-IPC)
2.- longhaul routes will be coach+PB (exceptions are those flown in narrowbodies)
3.- international medium range routes are all 2-class. If flown with 787 or 767, PB it is. If flown with A319/320/321, expect PE, with certain exceptions such as LIM-MCO, LIM-CUN or LIM-LPB, which are flown in 100% coach config

keep in mind this is a general rule of thumb... I'm sure many people will be able to point out some more exceptions