Hiya,
Sounds like this German Shepherd really is a handful !
I have a Japanese Akita and had him done when he was around 10-11 months old (he's now 30 months) to be on the safe side. We've never had a dog before and doing all the research, we definitley thought it best to have it done, just in case he turns out to be a 'bad akita' - Thankfully, it seems he's a 'good akita' and the op has probably made him just that little bit more docile. He only switches when he sees another dog and it seems he wants to play and check them out first before any hint of agression and growling happens. I even thought I should have left him as is, but glad we did do it.
If Samson is already quite hyper then it seems he'll still be hyper afterwards but maybe not as much and as he grows and matures will settle down more. I've definiltey noticed a change in mine in so much that if he meets someone new, he'll be excited for like 2 mins and then he'll chill out - same with other dogs, a couple of small jack russells around here are now his 'friends' !
Also, I think you may have an easier time afterwards training him as they respond better to training than Akita's - I never let mine off the lead now, he just will not listen to orders until he wants to, and I always used to hope he wouldn't meet a dog whilst he was off the lead else more than likely they'd have fought!
I'd also suggest getting a body brace (forgot the proper name !?!) as it means you can control them a bit better -
I do remember coming across one german shepherd that was muzzled and had an electronic shock collar too, the elderly owner saying he was completley vicious and attacked anything he saw. By using the muzzle and the shock collar, he said he could control the dog enough to take it on walks. I hope your doggy doesn't become as bad as that, but it's an option to at least have the dog and not have to put him down (which is what this owner had thought of previously)
Good luck !
Cheers, DtM! West London & Slough UK!