I’ve personally gotten bigger strength and size increases with an upper/lower as what I consider an intermediate than I had as a beginner and even a newb with full body. I would say eat like mad, and follow this template
Upper:
main pressing exercise bench works nicely here 5X5 or 4X6,
secondary pressing exercise normally a incline press3X8-12
horizontal pulling 4X6-10 or rep max this should be a heavy barbell exercise
vertical pulling or dumbell rowing 4X12 short rest (45 seconds)
rear delt exercise can be anything, rear delt raises, face pulls, seated db ‘powercleans’ ect just burn the life out of the rear delts and progress
optional curl/long head of the tricep exercise (Like a PJR or deadstop tricep extension) do whatever just beat the previous numbers by reps or whatever
lower body
Squat variation (high bar, low, close, medium, wide, front, just stick with it for a long time and progress) 5X5
hamstring/glute exercise must be a hip hinge 4X6-8
hamstring knee flexion exercise (leg curl or similar) 3-4X10-12 low rest period
quad exercise barbell hack squat, barbell hack rack pull ect leg press machine, hack squat machine, 3X15
abs 3X12 must be weighted
calves 3X20
Upper body two: same thing basically maybe slightly different exercise selection stick with an exercise atleast four weeks preferably six-eight
lower body two:
deadlift variation (conventional, sumo, rack pull ect) 4X6
front squat 3X8
hamstring/glute hip hinge exercise 4X10
calves, different exercise as last time
weighted abs similar as the first lower body 3X10
I want you to at least use the same exercise for four weeks, 6-8 is best, rep ranges were guides.