Yes, everything in the drivetrain is different. Mounts, engine, tranny, ECU, all of it. The SE-R isn't just another variation of a base model Sentra, it's entirely different aside from sharing the same body and chassis. The suspension, engine, tranny, ECU, mounts, bushings, shifter, seats, wheels, tires and dash are all different from every other version of Sentra or 200SX.
Putting an SR20DE or an SR20DET in a regular, non-SE-R 200SX or Sentra is a huge PITA. You have to swap EVERYTHING out. You would be better off starting with an SE-R and going from there.