I’ve done one self implant and had another done by a piercer both where painless minus the initial “scrach” so couldn’t tell you on that.
The idea is it sits below the skin above the fascia this allows the implant to be ‘isolated’ from bone and muscle and provides protection from both internal and external factors.
The likelihood of punching through depends on alot of things including experience and technique if you research and follow the great guides fro DT its unlikely.