I`m glad you have decided to neuter. The hormones will take about 8 wks. to fully decrease. You and your dog will both be much happier. If you free-feed, just measure out the day`s portion.
Many rott owners wait until the dog is OFA certified at 2 years old and do it at the same time. As far as the implants go, I`ve only heard of that for people that are trying to sneak their dog into the show ring. Neutered dogs can not be shown.