Bulgarian? Born and raised here. I spent 27 year on the platform and ended up with 14 world records. I trained with some of the all time best in the sport, Anthony Clark, Jim Cash, John Inzer, Tiny Meeker and was actually ranked #1 and #2 in the world in two different weight classes in 1 year (2275 total). Conjugate is a training protocol used presently by Louie Simmons. GPP, is just part of it. GPP is general physical preparation and this is a phase you do before entering into your competitive phase. Many do more strong man type activities and a way to get the body prepared. Sports specific lifts are not done. However, power cleans could be done.
Now as for carry over......does the knee extension have any carry over to the squat? NO, very little, how about the leg press? A little more that knee extension. Yet how many powerlifter waste time in the gym doing them both? The bench press used the sagittal plane of movement, meaning the motion/load goes from back to front (chest out). So does the incline bench help? Absolutely not, the plane of motion has changed, transfer of strength is very poor. The overhead press uses the frontal plane. When you change the plane of movement the strength increase diminish in their capacity to transfer over. So good powerlifters learn to maximize their time in the gym using ONLY exercise that will directly benefit the core lift. The explosiveness of the clean does nto transfer over to the squat, other wise Olympic lifter would be doing low bar squats as assistance exercise for their competition instead of high bar squats or front squat. The load travels in a slightly different path meaning the stress is on different muscles. Shane Hammon tried to make the conversion to a Olympic lifter years back. He was good but never rose to the top. He had a lot of trouble making the transition from powerlifting to Olympic lifting.
Now, I never said the only thing you do for powerliting is the three lifts did I? I simpley stated that according to the law of specificity you have to simply train like you compete. Training to be an Olympic lifter will not make you a good powerlifter. So you do assistance work that is as close to the core lift as possible that way the transfer of strength from the assistance exercise is very good. Olympic lifters do the same. Arched back good morning? Same as the lockout on the deadlift. Close grip bench, same plane of movement as the bench press. JM Press, multi joint exercise for triceps that is the same plane of movement as the bench press. Board presses, same plane of movement. High and low box squats, same plane of movement as the squat.
You can go ahead and do all the Olympic movements you wish, I do remember Fred Hatfield doing a vertical jump test against a Russian Olympic lifter and he won. Obviously powerlifters are very explosive. If you are wanting to increase your explosiveness, f=m/t, as I suggested speed work using your core life. 40% - 50% of your max with rubber bands going 10-12 sets of 3 reps. Force can be increased in the same lane of movement you use in your core lift meaning it will have a direct transfer. Same with the squat and deadlift.
Olympic lifts require a whole lot of very specific technique. As a strength coach or 25 year I taught these lifts and know it took 2-3 years to develop sound technique. Now when I trained with Anthony Clark, he did a hybrid conjugate method. He would do his core lift and ALWAYS did 3 heavy single just like a meet. Then he did more of a repetitive method training for the assistance muscle groups using multiple sets at 8-12 reps. Very similar to how Louie Simmons trains his guys at West Side.